I used the fault finding guide as found by Centurions and decided to look at the batteries in the sender unit fixed to the bottom of the door. I checked them with my multimeter and they were showing 3.5v as they should. I put them back in the sender and lo and behold the door worked properly using the remote controls. But it still didn't work using the main control box. Rang Gliderol again and this time they gave me a contact in Rochdale, DR Garage Doors. Spoke to the owner, Dave, and he said the problem would still probably be those batteries and gave me a website to get a good deal for new ones.
I've ordered them and they should be here in a couple of days.
Just want to give a reccomendation to Dave at DR Garage Doors. Helped me with good advice, friendly, and didn't try to get any business out of me with no good reason. If the new batteries don't solve the problem then I'll definitely be contacting him again to do the repair.