Hi I managed to source a new digitiser on eBay however when I took the A5 for repair locally they refused to repair it as they said that separating the broken digitiser from the original (working) screen would likely break the screen. Has anyone had experience of this? Do I also need a new screen and then somehow attach the new digitiser to it?
Or has purchasing a digitiser on its own been a mistake?
This is true, separating it can very easily break the screen. You need patience and care to do so. If you're afraid to do so, or are weary about breaking your screen, then you should purchase the full set; LCD + digitizer, which is what I did when it came time to replace mine (and, just for shits-'n'-giggles, I tried to separate it after, VERY easy to break). If you are fine with a crack, can still use the screen if cracked, still have an image after, you can just replace the digitizer. Note that the best way to do so is to solder wires from the new digitizer to the old digitizer ribbon which you can cut (see here
for idea). I'd say you can still do it, if you're careful. Do it in a quiet place, so that you can hear any crunching or cracking that may or may not occur. If you hear any crunching or cracking, STOP. You will break the screen, it's not coming off easily. If you don't, keep peeling away.