So Norfolk line to the rescue it is then ...

I tried to get information out of the chunnel people today and they couldn't tell me what was happening in the way of when we could travel. Apparently they are now trying to get all the booked passengers on the few trains they have which could mean we have to travel much later or much earlier than we can ... They are currently running one train every 2 hours and stopping in the evening instead of going on through the night (which sounds like carnage really).

So I decided to book with the norfolk line just for back up (it's only cost £21 which is much better than not going !)