sylonien I have a good contact in North London if you need it fitting: With the wiring You're looking at about 10 hours labour which I think would put it at £250 at the most.
I'd also recommend you did some sound deadening which would be an additional materials and labour cost of course.
Previously: 2003 Peugeot 206 1.6 8v | 2006 E90 320d M-Sport, 19" BBS CH, Full Ice-cold JL audio install, August 2010 Total BMW 6 page feature car. | 2003 Nissan 350Z GT Coupe 286BHP
Now:2010 E92 LCI 335d M-Sport