Mechanics and Fixing Any Questions Answered

Re thinking, if you flip the rear wheel round won't it be dished completely the wrong way and not fit at all, the freewheel might also catch on the stays?

Almost all wheels should have no dish at all, so if it's all off to the opposite side then it has some dish and is wrong, if it's off to the same same side then it's more likely the frame is off, both could also be true but it's an easy thing to check first. An easier thing to check before that is that you haven't got the QR skewer springs on wrong.