"Club" price, with discount, appears to be around £120, delivered (normally £125).
You could get them cheaper from the US, depending on the exchange rate and if Customs pick them up!
http://shop.ebay.co.uk/i.html?LH_AvailTo=3&_trkparms=65%253A12%257C66%253A2%257C39%253A1%257C72%253A2471&_nkw=scangauge&_trksid=p3286.c0.m14&_pgn=1" onclick="window.open(this.href);return false;
Some of the US offers includd extras, for example another cable for a 2nd car.
In the UK, this place seems to be as good as any to get them for £120 (with club discount):
http://www.autocaress.co.uk/acatalog/Scan_Gauge_trip_computer_gauage.html" onclick="window.open(this.href);return false;
The cable length is 6 foot.