I have a 1985 Range Rover Vogue auto which has been the family since 1986 and about to upgrade the carburetters to a Weber to make it more efficient. I also need to replace the waist seal mouldings on all 4 doors, but find that they are no longer stocked. Hopefully somebody on this site will be able to direct me to a supplier.

Welcome. Definitely worth the carb upgrade if it is a high comp 9.35:1 and it sounds nice too.

http://www.ebay.co.uk/itm/V8-Land-R...ender-Cobra-/192138720509?hash=item2cbc5c34fd
This is the unit that I am considering, but think that my engine is an 8.13:1, so assume that it will make a big difference in performance and not too sure as to what the average fuel consumption would be.
Any suggestions as to where the waist seal mouldings can be sourced.

8.13 CR is the main restriction with your engine unfortunately. But if you want to buy a carb upgrade, please don't go to RPI.
Just about everywhere else will be cheaper, realsteel / v8 tuner, but a quick search has turned up kit car supplier, roadcraft as looking competitive. Vat here is +20%
https://roadcraftuk.co.uk/index.php?route=common/home

Also, your fuel pump may need an upgrade.

Best start a thread in the range rover classic section for the biggest audience. Not many will find your query here.
https://www.landyzone.co.uk/forum/range-rover.10/