BMW parts are expensive here, and if not in stock, they import them from Germany so there's a delay. For some garages, they will only use parts they have supplied as well. If you have a friendly dealer from the UK, you could ask them to ship parts out to you. I've done it a few times with Cotswold Gloucester and they've been great. Most of the time, even with shipping, it works out cheaper than here. Doesn't help with tyres though so best to get them replaced before leaving.