Really? You can find a hotel for £68.29 per night which includes all food, unlimited soft drinks and alcohol with meals? That's in an area with a wide range of touristy things to do (as the ship will be docking at various interesting locations versus a hotel in the middle of nowhere)?
I toured the UK for two months last summer and never paid more than 60 GBP per night and in many cases under 40 GBP. Granted that none of those included evening meals or alcohol but some included breakfast and an evening meal and a beer isn't much extra.
Per person for a couple? I think you can start to get pretty close aside from the bigger and more expensive cities. I'm pretty sure you could do a walking trip in England for not that much more. And keep in mind that's the starting at price. Also, the UK is expensive. You can absolutely do trips to other parts of the world for that sort of money.
If it's the sort of extended trip someone is into, it might well be a decent deal. But it's not an absolute bargain relative to other alternatives one could put together.