After getting a near £500 quote from Brittany I have now got one from Eurotunnel for £144. This is through Carefree and before 0600. I was concerned about gas regs but apparently it is no problem with Calor. Hope this helps others on atight budget.
See the posting under Camping Cheque - we used them to book with Eurotunnel - going out Friday night at 11.30pm (time suits us because we travel down from Yorkshire) and back on Sunday morning at 9.30am (again to suit us because our last night is in Calais). This, plus fourteen Camping Cheques cost
Have you thought about the tunnel - it has good offers for certain sailing times and last year we stayed overnight in the carpark at the back of the filling station on the way out from the tunnel (but still within the compound) We were directed there by reception staff and there were just a few other lorries there - no caravans - but a good night's sleep.