It’s worth working out how much you use it to see if that alters your budget.
We use ours quite a lot (2 pre-school kids) so it was worth spending a bit more up front for a more energy-efficient model to save in the long run.
e.g. we were picking between a B efficiency and an A+, which were £199 and £339 respectively. The sums for us went like this:
B model consumes 4.48 kWh per cycle, so ~55.73p a cycle or £144.90 a year
A+ model consumes 2.68 kWh per cycle, so ~33.34p a cycle or £86.68 a year
There are a couple of site to help with working that out, try reevoo.
In the end we went for this one: http://www.beko.co.uk/Item/DPU8360
Been pretty happy with it.