I find with sliding mitre saws that they are often let down by the blade being able to wander because the sliding mechanism either isn't stiff enough or the bearings have play, only real test is to get your hands on it and give it a bit of a twist – bringing the blade out to full extension and dropping it down as you would to cut and seeing if it can wander side to side or twist either way. I've only ever found one budget slider that behaved well in that respect, an end of line B&Q own brand one I bought about 5 years ago and which clocked up over three years of active service, but since then everything I've tested for less than £500 has been pretty disappointing and instead I've opted for non-sliding saws with bigger diameter blades instead to get accurate cuts and still have a fairly decent capacity.
Broadly I think Erbauer stuff is pretty good though – the right balance of reliable and disposable, ideal for site work where your more likely to have kit knicked than wear it out. But with a sliding saw from Screwfix you're not going to be able to test it without buying it, for the same sort of money I got a non-slidey Bosch with a big 14" blade instead which cuts absolutely true and is much more robust. Easiest place to get you dirty paws on a slider test its accuracy and quality is B&Q, as they have all their stuff sat out on display.
