I have a 2002 VRS and the power steering develops a noise and becomes a bit heavier after about 30 mins of driving. I have checked the power steering fluid today when the car is cold  and it's over the max by quite a bit could this be causing the issue ? 

Should I drain the system completely and refill it and bleed it or just drain the excess out ? 

I would drain it and refill with correct fluid.

And check for leaks. I think a wrong fluid topup during my early days rack leak helped speed up killing it... wrong fluidor too much can over pressuerize the system and blow the seals.

Certainly drain the excess and see if things improve as a first step. PAS fluid expands when hot, which is why there are 2 marks on that dipstick.

 

After that, if it's still "not right" (changes in weight with distance driven, "funny noises" on lock...) yes drain and refill.

I've drained the excess fluid out but has made no difference so ordered some more so I can drain the system and refill. What would be the best way to drain as much of the fluid out of the system as I can before refilling with new ? 

If you are careful you can do the following as an easy way to flush - you need a helper though

 

disconnect return feed to tank and put in a milk bottle.

 

run engine for around 3 seconds until ps reservoir is nearly empty

 

switch off engine and refill ps reservoir

 

run engine again for 3 seconds and then switch off

 

when you see fresh fluid being pumped through to milk bottle switch off again and reconnect return feed

 

just a case then of bleeding system by going lock to lock and topping up as required.