I couldn't say, but it seems good value.
The advantage of a 'proper' screen can be the optical coating if it has a gain greater than zero. This can give the image more 'punch' than a painted screen, so may be better. Especialy if the pj is a low lumen one.
Is yours the 2100 lumen model? If so, I would think that you'd be fine with the paint, but for the sake of £60, it wouldn't hurt to see what the proper screen is like. Does it say what it is meant for? Slide or Cine film screens tend to be very grainy if the one I used was anything to go by.
Gary.