I'd recommend you take a look at what lenses you have and think about if you'd be happy if those were then "true" focal lenghts (so no more multiplying x 1.6 because of the crop sensor). Keeping in mind all EF-S lenses would not be fit for full frame (they only cover the smaller sensor).
A used 5D mkII can be had for £400 in good condition for example.
I'd recommend you take a look at what lenses you have and think about if you'd be happy if those were then "true" focal lenghts (so no more multiplying x 1.6 because of the crop sensor). Keeping in mind all EF-S lenses would not be fit for full frame (they only cover the smaller sensor).
A used 5D mkII can be had for £400 in good condition for example.