Made some discoveries underneath the bunk.

I had the bunk lifted the other day to drain down the system. I took the opportunity to have a poke around and familiarise myself with what lies in there. 

The first thing I found was what looks like a spare pump. It appears as if it has never been fitted and I wondered whether the previous owner kept one there as a spare?  

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This looks like it might be the one it would replace. Question is, what is it?

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Then I noticed a couple of spare electrical connectors, I followed them back and they are connected to the back of the fresh water fill point. Where should these be connected to?

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Apologies for the multiple question post but, I thought it would be the best way to go about it. My last query concerns the hot air ducting. There are two lengths of trunking that make their way forwards, one, the thicker one,  must be to the shower cubicle. But where does the smaller diameter pipe go to. There is a vent on the step-through from habitation area into the cab. When the heating is on no warm came from it, only a waft of cool air, I assumed it was maybe a vent. Should it be warm air supply?

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Many thanks for taking the time to look.

The item is a solenoid operated water valve. Energised open, spring closed at a guess
Another guess is was where the two wires are now so was a solenoid valve to let water into the system, I'm guessing it has a Whale water system. 
Another guess is that the small air hose is an air lint hose for the heating system when running on gas, if so definitely nothing should come OUT of it.
I had a Warwick Duo which, thankfully didn't have the absurdly complex Whale water system....

I think your suspected spare pump may well be a solenoid valve and the two wires were the feed to it. If my suspicion is correct it would have been fitted to the back of the cold feed from external pump and  and shuts off fill when tank is full. If that was the case the previous owner has removed it for whatever reason and left it loose in the general location.
The smaller diameter heating duct does go to the outlet in forward step,it’s well known that not much comes out of this outlet.

Thanks for your replies. 
I did once try to add some fresh water from a bucket using the pump that fits onto the fill point socket. The pump did not run though. Could those wire connectors be the supply to that pump?  What about the valve in the second photo, it has "pressure switch" on the knurled part. What is it's function?

Your suspected pump is as others have said the solenoid operated water valve that fits to the back of the Whale external water inlet socket.  The idea is that to allow water to enter the inlet socket the solenoid has to be energised to open the valve and when the fresh water tank is full a float switch at the top of the tank cuts the supply to the solenoid causing the valve to shut and stop the water flow.  This is to allow a mains fed water hose to be left connected to the Whale inlet socket on a serviced pitch.  I removed mine as I didn't use this capability and it allowed the external Whale water pump in a barrel to fill the freshwater tank more easily.  It also removed the gauze filter which protected the water valve that became blocked very easily.  The external Whale pump will still stop pumping when the fresh water tank is full and I can still fill the fresh water tank with a hose until it overflows.

DaveyA wrote:Thanks for your replies. 
I did once try to add some fresh water from a bucket using the pump that fits onto the fill point socket. The pump did not run though. Could those wire connectors be the supply to that pump?  What about the valve in the second photo, it has "pressure switch" on the knurled part. What is it's function?

The wire connectors which should be taped up are almost certainly to connect to the removed solenoid.  That said, there must still be a power supply to the back of the Whale inlet socket to power the external Whale pump through two brass contacts.  It looks from the photo that they are still there.  Your pump may not have worked because the autofill wasn't turned on in the van, or, the pump was u/s, or, a fuse has blown.  

The valve in the second photo is a Whale Non Return Valve (NRV) and pressure switch.  When the water pressure drops in your internal water system the pressure switch closes causing the Whale pump in the freshwater tank to start pumping water into the system.  Once the system is pressurised the pressure switch opens which stops the pump.  The NRV stops water draining back into the freshwater tank.

Those two connectors are on the loom that is connected directly to the back of the inlet socket. They must need to pick up a supply from somewhere.

The back of my Whale inlet socket is difficult to access otherwise I would post a photo of it showing how it is wired without the solenoid valve and the two redundant connectors that I have taped up.  Someone might be able to post a photo showing how their's is connected with the solenoid valve and from this you should be able to figure out how is should connected without the solenoid valve.  Without the solenoid valve you have to make sure that the Whale inlet socket is energised when the freshwater tank isn't full so that the external Whale pump can work.  Alternatively you could reinstate the solenoid.

Many thanks, I appreciate the help. The van did come with a warranty when I bought it. I suppose I could take advantage and ask the dealer to sort it out. Although I would quite enjoy fixing things myself if possible. Saves the inconvenience of dropping off and collecting the van and also learning stuff about the systems. I worked on trucks all my life so it's not totally unfamiliar work.