I'm a new C1 owner so I'm sure that many of you will already know about the C1 parts supplier in Germany - see http://www.c1teile-shop.de/
The web site is in German but you can use any of the web translators to translate the pages to English. The most convenient translator is by using the Google Chrome web browser as it detects the language and it will translate it automatically.
I emailed the shop and asked about shipping to the UK and this is the reply:
shipping to England is no Problem.
Shipping costs up to 5 Kg are 17 Euro. Insured package with DHL.
You can send your order by E-Mail. We make all other one then by E-mail.
You can pay with PayPal or Bank Transfer.
So as you can see, he speaks good English and is is possible to pay by PayPal. Shipping costs are a bit steep but if it is a part that BMW can't supply or it's cheaper than the BMW part, it might be worthwhile.