Paul,
I've used JCW's fenders and, with a little care, it's hard to beat them for the price. HOWEVER, let's make it clear from the start that if you can find a used German fender in reasonable shape, you will be better off. They are a much better product, in terms of metal gauge and quality.
With aftermarket fenders, it's recommended that you replace them in pairs, as the cutouts for lights and their mounting holes often don't precisely match what's already on your car. The fender-to-body mounting holes can also be off, so plan on redrilling some, and welding/brazing patches over the oddball ones. A pair of aftermarket rear fenders I used had the bumper bracket cutouts misaligned by about 10mm, which I didn't notice until I had trouble getting the rubber bracket bushings in place. Since everything had already been repainted, repositioning the cutouts was not an option so I had to live with it.
It is also a good idea to strip the primer/paint off the fender(s) before topcoating, and treat it (them) as you would any bare metal body component (phosphoric acid and/or etching primer.) You may (or may not) be surprised to find rust underneath that factory paint, and it's easier to deal with now than in 2 years when it's bubbling through your nice new paint.
Hmmm, on second thought, maybe hoding out for that used German fender isn't such a bad idea after all ....
Al Adams