hi,I know this may sound stupid,but how can I tell if my water pump is working,as my engine is going to change the thermostat,flush the rad,and change the hoses,I need to top up the rad every weekend,at least 2litres,but I cant see any leaks,any help will be appreciated,cheers truewhite0

Pump and filler cap.

Remove radiator cap. Rev engine. If water appears to rise up the radiator filler then your water-pump could be working.
If your loosing 2litres each week it could be a head gasket [cry!]. However, I have found the filler cap can leak especially if its old. The steam/water escapes and evaporates. Try removing the filler cap and cut a replacement rubber gasket [old inner tube is ideal] to fit the caps seal. Alternatives slighty compress the filler cap's wings [squash with pliers] so it screws very tight onto the radiator. You could be lucky and a badly fitting cap is the problem with over-heating due to low water level etc.