Try doing a search on here as this has been covered a few times. Recaro Start is the best 1 yr - 4 yr old seat. Factory seats avail second hand but you will need the bars etc fitted to hold them.
Britax used to do a good seat - can't remember the model name though. Used it with a Halfords seatbelt tensioner - perfect for 18mths+. Used a mamas and papas rear-facing seat for the first 12 months. Bit of a squash for wifey in the back, but OK for short journeys.
TVRs seats come in leather and were covered to match the car they were sold with. So it maybe that you will want one to match? YOu will also need to ensure you buy all the bits - there is the seat, a bar and one or two bits of cushioning (AFAIK).
They do pop up in the TVR Parts section here quite often, or the classifieds on the club website / Sprint magazine. Was basically a recovered Recaro Start seat IIRC...
Gazzab is right, the seats are built for the car in matching leather. There is a large bar that goes through the floor and the seat is in two pieces. They are very good, but it will be hard to find a seller I think.
