Thanks for the replies. Sounds like something worth investigating more then. I did a bit more reading and I think rear facing seats would be legal from a DfT/DVLA perspective if they had either a) three point belts or b) lap belts with car seats that have their own restraints, or c) ISOfix...

Hi there, former Stage 1 driver here (I didn't need to pay for the fuel thankfully!). Now have a young family and thinking about maybe getting a Series as a second car, for getting out in the local countryside etc. Don't have one yet though I've been closely following all manner of eBay...