Have you tried your local dealer? You may be surprised how cheap stuff can be if you pal them up a bit?

You know the electric window switch pack that fucks up? about £80 second hand from everywhere? I just got it for my P38 from Hunters in Guildford for £109 + vat. Worth paying a little extra for a genuine, new and guaranteed part

Alternatively, this is only a small business and they specialise in the EAS but you never know:

http://www.p38spares.co.uk