Sorry to hear about your loss mate...
FYI - you can easily pick up a Golf R/S3 engine for around £1300-2500 price range depending on how many ancillaries you require (manifold, injectors, wiring loom, turbo, oil cooler, etc..). Some even include a 90 day warranty. In your case I'd recommend you source a pre-owned engine and visit a trustworthy independent VW specialist for the engine swap. Factor in around £2K for the engine, approx £1-£1.2K for the engine swap labour and some extra ££ for other OEM parts and ancillaries you might need from TPS. Total cost would be around £3.5-4K which is a decent amount of saving over dealership prices - but at least you'll have peace of mind with the competence of an independent and the fact that whatever you are promised will actually get done.
I'd steer well clear of a dealership given their work ethics, accountability and the ball ache they are to deal with when things go wrong (and they seldom do). But hey, that is just from my personal experience with dealerships, YMMV.
Good luck 👍