Broadway Bench/Bed Runners

I don't know the proper term but the drawer like runners on one of the bench seats/bed of our Broadway need replacing. Spoke to A/S parts dept this morning and the lady found them in their catalogue, she initially told me they were £11.?? each + VAT + postage so I said I'll have a pair please.  She was totting it up  when she realised she had given me the wrong price, the proper price is £29.99 each + VAT + postage which is £76.97. I decided to look elsewhere. I've checked ebay and found some 40cm and 60cm ones but I need 50cm. So do anyone know where I can get some please?

Screwfix have some for £6.79 a pair.  They look like they will do the job. I am going through the same process but will probably fit something with a higher load rating, whether the extra cost is worth it is debatable though.

The Screwfix ones are 45mm deep and the ones in the Broadway are 17mm but I might buy them and see if they work. Thanks GROUNDHOG.