Just thought I'd report back on my experience of Eurotunnel - well, it all works well but it's a bit weird!
Cycled from the Camping and Caravan Club site in east Folkestone (up a v steep hill) to the pick-up point at Holiday Inn in west Folkestone, at the crack of dawn literally. At 7:45 a long wheelbase white van with extra windows turns up - it was for me, and just me. I was the only person using the service this morning. Bike was tied up securely in the back, I sat in the front. There's room for 7 cyclists and bikes. A bit of a wait to get on one of the rather sinister trains, then another short wait till it set off. Strange sensation, being in a moving vehicle which isn't being driven! 35 minutes later we're in France, and by 10am French time I was dropped off in a car park. So that's about an hour in total, probably the quickest you could do it.
On the way back we had a much longer wait for a train. I was picked up at a bit before 6pm, and was dropped off near the campsite at a little after 6:30, so taking the time difference into account, about 1 1/2 hours. This driver (a personal chauffeur again!) told me lots about Eurotunnel, including that it can take a great deal longer in busy holiday periods. It'd be worth asking them when you ring.
I'd definitely do it again, and those times worked fine for me. The drivers are very helpful and may be able to drop off at the rail station, for instance.
“My two favourite things in life are libraries and bicycles. They both move people forward without wasting anything. The perfect day: riding a bike to the library.”
― Peter Golkin