Hi Niall
Basically there are no vintage parts suppliers in the UK, but all parts used in modern Airstreams are supplied from international suppliers and we actually have much better availability of those parts than the US, plus you can fit 240v versions.
There are several high end restorers (like American Retro Caravans,
https://www.arcairstreams.co.uk/?fbc...ZzvOOT2n2gmeNc, and Retro Vintage) but those folks don't supply parts, only do rebuilds.
Just keep in mind, every Kg of weight you add is another Kg you will have to drag around and older trailers have cabinetry that appears 'flimsy' to keep the weight down - its why modern units are made with lightweight not domestic ply/timber (take a look at Morland's for ply,
https://www.morlanduk.com/lightweight-furniture-ply).
- Martin