I bought an ex display version of
Route 66 which included a SirfStar III receiver and I find it works well with my N73. A full licence for 3 phones and all the stuff included in the kit was included all for £39.95. (Great bargain from an auction site!) To work with my N73 I had to download an update from the Route 66 site and transfer the files from the MMC onto a mini SD card. The kit in the link would work straight from box with N70 though I think.
Once the receiver is connected with the phone and getting signal from sattelites I put it in the centre console of my scenic with the lid closed and it works fine.
I find the voice directions spot on but the map can lag slightly. I've never used any other sat nav so can't compare with another product but for my needs it's brilliant as I go by voice rather than map so I don't need to take my eyes of the road.
Edited as linked to Europe Kit not GB kit.