Cost estimates -- £150 covers it

Been checking out some costs:

The Eurostar is showing on their website £45.50 for several selected afternoon trains. (This is the non-flexible cheapest ticket). (via eurostar.com)

The ferry is showing as £24 with bike via www.transmancheferries.co.uk

A random punt on Expedia suggests that about £80 per room should fit the budget.

So, single occupancy hotel looks like the budget is £150, most of which is the hotel.