Start button and other questions

[Nobbles]

I am looking into buying a 7 having had previous ownership of a westfield years ago. Since I have gone through, the Elise, Boxster and BMW phase. It is now family time and to get a family car but to keep the fun and have a 7 in the garage. I want to buy now - I preume it is cheaper and can spend around 15k. I am keen to use the car as much as possible and I am now based in France which makes the summer longer.

OK questions - there is a roadsport just come up for sale on Pistonheads. If you have a start button does that mean anyone can start the car or there is a key operation also?
Is the K series reliable? It was on my Elise, but you do here the tales?
Is 120hp enough?
Are 5 point harnesses good with baby seats - can I retrofit the normal seatbelts?
What are the items to be checked?
How often for a service etc?
Anybody registered a caterham into France?

Thanks,