If you visit this website http://www.noonsite.com/Countries
you will find a lot of useful information about what you need sailing in different countries. Since you somehow, somewhere must cross the English Channel, where the current can be very strong and there is much traffic in the waters, I will suggest that you select a boat that have an engine that can bring you across the channel in the first place, in case the wind and the current are contrary.
The tidal difference quite large in some places, both in France and on the channel islands, so you will need to plan carefully and be able to calculate the tide both for the port you are leaving and the port of arrival.
On the southern part of the french Atlantic coast, in the Bay of Biscay, there are very few ports, so you must be prepared for sailing around 100 NM from one port to the next. You should absolutely get a pilot-book for the areas you want to sail, like Reeds Nautical Almanac.
I am not very well informed about the prices on boats in UK, but I assume they more or less are close to the prices in Norway. It seems to me that you probably will not be able to get a boat larger than about 24 feet. The bright side being that the cost of calling a port is calculated by the length of the boat.
But I suggest that you first try the inland waters of the Netherlands and the Northern part of the English Channel before you decide to Challenge the Bay Of Biscay.