I got mine installed through the Energy Savings Trust in August 2013, might be worth checking if they are still doing it. Although I can only charge the Ampera at 16 amp they fits 32 amp units to future proof the installation.
I had a BG homecharger fitted to my old flat about 2 1/2 years ago. Great experience.
I recently moved and went with British gas again, paying £250 for the 32a untethered model. Last week I cancelled my British Gas installation, they refused to fit to an older style consumer unit (which I agree with as no RCD protection) despite them being told about this prior to the installation. on the last install they provided a garage style consumer unit so I thought the same would happen. I offered to either upgrade the entire board or provide a garage style board for the charger from the existing isco block - The electrician agreed and said he would come back when the work is complete.
Anyway, they kept calling several times a day for several days asking when they'd be able to install despite being told that my electrician isn't starting the work until next week. After receiving about 10 calls from them and me explaining this on every occasion I decided to cancel the order entirely and have my £250 returned (which has turned into a faff).
I'll be going with one of the smaller local installers instead. Shame because it was great service the last time.
I had British Gas do mine I payed £99 for the 32amp. The engineer dropped his drill on my kitchen top and damaged it you can't really tell it's damaged but I got a cheque back from them for £450 to replace the top which I have put off doing So well looked after with British Gas