cumbrianboy,
I'm tired now, it's 2130 hours now here in "Basingstoke", one is never going to successfully plan on checking in at STD - 30 minutes (to the second), that the route (block to block) will take 1 hour or less and then a transfer to the rail station in 15 minutes with absolutely no waiting time for a train.
My background is scheduling and never in a million years would I suggest to the honest folk of Carlisle that they could be from their front door in Carlisle to a rail terminus in London in less than 3 hours!