I agree about getting the mooring before the boat.
As Alan says, a steel boat for your budget is likely to be a dodgy proposition.
A fibreglass cruiser will be a sounder buy.
Asking prices are from £900 for a bare shell. (There is actually a 22ft Dawncraft advertised on Facebook in Leeds for this amount) to £15-16K for a good 'un.
If you are just going to cruise the broad canals, you don't need to be tied to a narrowbeam, but bear in mind that over 7ft beam attracts a surcharge on the licence fee.
Look for a boat that has heating, hot water, solar, decent cooker and with a current BSC.
You can expect a boat well kitted out with comforts that will be within your budget.
As to engines, my preference is outboard, but quite a few grp boats have inboard diesel or petrol engines.Some have a Z drive on the transom which I don't like, and some the engine is inside with shaft drive which I think is ok.
If you have specific questions about engine type, or boat make, just ask.
For me, I like Norman and Freeman the best, but not Dawncraft (apart from the Highbridge) as they have issues that other grp boats don't have.