Alors, c’est très facile!
All you need to do on the UK side if you're returning to your own strip is to inform Customs four hours before your planned arrival.
You can use the GENDEC form (see these pdf
versions) or you can simply ring them up on +44 870 785 3600 and give them the details of your return. They've always been very helpful when I've done that. You can even email them at email@example.com
Lydd is good for VAT-free fuel. If you can be bothered with the paperwork then doing a normal drawback claim will let you get money back on everything in your tanks as opposed to just the fuel you buy at Lydd, but I tend to feel that life's too short for the difference to be significant and so simply go for the VAT-free option.
Drop into the aero club too - a friendly spot with comfy chairs and usually a pot of coffee on the boil.