Drum Jammed - Won't Turn

Hi,

I have a John Lewis washing machine and the drum is completely stuck (Model number: JLWM1405).

I've read on these forums quite a bit, so have looked carefully all around the drum to see if I could see anything caught or poking out of one of the holes, there is nothing as far as I can see. I've checked and cleaned the filter and there was nothing there either. At one point I did manage to get the drum to turn a little, but it just gets stuck again.

I'm thinking maybe there's something stuck that is stopping it turning, but I can't see anything and don't understand how anything could have gotten in there anyway.. Should I take off the back of the machine and check the sump hose? What do do?! Please help!!

Thanks...