Well I'm slowly getting there but not quite! So I followed those instructions and GMIC now is in the list of filters - however where as all the other filters are in black and can be clicked on, the GMIC one is written in grey and nothing happens if you click on it!
After typing the above I suddenly thought I'll try and open gimp from one of my saved photos. When I do that GMIC is there - so I thought yipeeee all sorted but then within a couple of minutes gimp stopped responding and I got a message saying:
Plug in crashed
The dying plug in may have messed up GIMPs internal state. You may want to save your images and restart gimp to be on the safe side.
I've restarted it and when there is a photo there GMIC is there to be used - but unsure if it will keep crashing until I test it more! My laptop is off for some repair work tomorrow so don't know how long I'll be without it but will try to use the GMIC filter afterwards again. Thank you so much for the help - at least GMIC is there now but don't know if you have any tips to stop it crashing!