Current install cost

[FB.]

Just as a rough idea what would you expect a 2-2.5kwp system to produce a year, we are in the worst part of wales for weather but a rough idea will help me

Look it up here, and once you've put a marker on your location, select the Climate-SAF PVGIS dataset rather than the Classic PVGIS from the upper right drop-down tab:
PV potential estimation utility

Probably about 2500kWh per year for an ideal roof, and less if the roof is not South, or has some shading, or has a strange angle.

You'll get, in total, 18.25p (16p FiT and half of 4.5p export tariff) for each kWh generated.
You'll save about 13p per kWh for each unit of electricity used in your house. The exact usage varies from about a quarter to half, depending on the way you run your appliances during the day.

So "best case" gains in year one would be about £450 in FiT payments and £160 in bill savings.

 

[FB.]

Just as a rough idea what would you expect a 2-2.5kwp system to produce a year, we are in the worst part of wales for weather but a rough idea will help me

Alternatively, borrow Gavin's link in his signature and find your way to the price/payback calculator for value/high-spec/ultra solar arrays.
The outputs will be in accordance with SAP-2009, so should be more like the minimum to expect from a well-installed system - assuming no major shading issues.