It's really a piss poor service - the onboard "train managers" are generally pretty good, but the jobsworths at St Pancras seem very hostile to bikes on their precious trains. I was once threatened with an £80 fine by a pillock in a peaked cap for daring to arrive in London with my bike before 10am on a train that was less than half full (for the whole journey, I was the only person sitting in the coach I travelled in).
High speed trains in general are not always all that tolerant of bikes. It seems that trains are good when they are in the middle - semi fast, regional or local and you are fine, high speed or undergound and you might experience problems.
I was thinking of taking my bike to continent in summer, and afaik Eurostar will take it 24 hours later as it does on a van, not on their trains. I thought the TGVs were also quite restricted, but I saw bike space (unused) on the TGV I took from Lille to Paris in March. I was going to draw up a list - Thalys, FYRA, AVE, ICE, ICN and so on - has anyone already done this?
Also, we should be asking as cyclists what provisions are going to be made for us with hs2. Maybe that's for another thread, but consider:
1) Will the trains take our bikes?
2) Will there be adequate parking at stations. Remember New St has 26 spaces at present!
3) Will there be a network of paths around the stations - especially Birmingham "parkway"
4) What about the existing greenway that is going to be severed?