Bonneville Brake Disc

Or if brands are unimportant these are £80
http://www.squaredeals-ltd.co.uk/bo...00865cc-upto-2009-front-brake-disc-5707-p.asp
and made in Blighty from decent material.

 

Welcome to the form Bensley.
Firstly I would get the disc checked to see if it is actually warped, this can be done very easily using a dial test indicator if you have one or know an engineer/mechanic who has.
Failing that use a piece of plasticine or blu-tac with a little pin stuck in it and position the pin very lightly on the side of the disc where there are no vent holes.
Slowly rotate the wheel and very carefully look for any run out on the disc to the pin.
You should be able to detect within a few thousandths of an inch using this method.
If you do have to change the disc, check Wemoto out, they do EBC and I personally would fit new pads at the same time for what they cost. Full strip and clean it'll be like new.

 

If you check the disc and there is no run out, that indicates that both your hub and your disc are okay.
The problem could be just a build up of shite in your caliper which is not allowing your brake pads to move freely.
Check out Delboy on YouTube for cleaning and lubricating the brake calipers.
Good practice to strip and clean your calipers twice a year, have a set of new pads ready to fit at the same time, you could find that it solves your problem, if it doesn't we can look deeper, the time spent cleaning and maintaining is certainly not wasted, it is amazing how much shite and corrosion gets into the caliper assembly.