Leisure Battery Change

Bit of advice please. Currently have a 105 amp battery in my Sussex Duo that is over 4 years old and sometime in the future I will need to replace. My plan is to fit a125 or 135 amp battery to replace , assuming there is space under the seat to take that size. Are there any do' or don't's that I need to be aware of. The reason for upgrading is that we wild camp quiet a lot, and there is no room on the roof for a solar panel to trickle charge the L/B.( aircon unit in the way)
Thanks

Can't think of any issues as long as it fits ok and is properly secured.

Are you sure you can't fit solar?  You could probably fit a nice 100w flexible panel above the windscreen which would keep you topped up nicely.

You can always run multiple panels in parallel too (for example 2 x 50W panels) which might fit easier.

I helped fit a 140w flexible panel to my friends old VW T25 van last weekend and it didn't even take up half his roof area.

This kit uses 2 50W panels that are only 28cm wide:
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Thanks for that Noggin. Will certainly look into the possibility of fitting this system. Price is good and seems quite easy to fit.
Regards

Neil