In reply to Richard Carter:
Having had a quick peek at your profile it looks like you're a keen cyclist so I doubt that you'll struggle with the c2c in a day. I did it with a friend Tim almost 2 years ago and really enjoyed it. I was in pretty good shape but as Tim was a really experienced cyclist with loads of long bike tours under his belt along with years of doing a 16mile daily commute I thought I'd best do a bit of training so as to not let the side down. I racked up a number of 40-70 & a few 80-100 mile rides in the 2 or 3 months leading up to it, but rested the week before. We bashed through the 160 miles from St Bees to Robin Hoods Bay no probs in the end, although Tim did have problems trying to refuel after about halfway so I hope that's not something you struggle with. Don't think it helped matters any that on the day I devoured multiple sandwiches, soreen, chocolate bars, fruit, flapjacks and even a fish supper.
We were lucky enough to have Tim's bro Sam meet us at 4 points throughout the day/journey and he had our gear, food & tools in the car so we were able to ride our road-rockets instead of our commuting/touring bikes and travel light which made a huge difference. On the down side we actually started the day from RHB as that's where Sam lives so we drove the full route in reverse before cycling it (with a 4:30am start) - seeing the distance we had to cover was quite intimidating.
FYI, and so you have something to aim for - the ride took us almost exactly 12 hours (about 10.5 hours saddle time).
Best of luck mate, let me know how you get on.