There's a resolution and here's what happened:
I was going home (London) for the week to visit my parents (as I live at Uni) so I brought my gun with me as there's an airsoft shop nearby. I took it in and the shopkeeper took a look saying he gets many gbb pistols coming in with stuck slides however never a gun with literally no movement of the slide 1-2mm wobble of the slide. He tried wobbling every part of the gun for the next 10 mins. Last option was the vice and hammer, I had no other options so I let him try with the warning that around 50% of guns will be ruined and need few to many major replacement parts. The wobble could actually reset the trigger so I wasn't to worried about the lower.
The frame was clamped to the table wrapped in a cloth and the slide was slowly and lightly knocked with a dead blow hammer under another cloth. After some knocking and fiddling with the recoil spring guide, the slide remained fixed as if frozen in time. We're half an hour in and nothing has changed, things were not looking good. But as he persevered on his supporting grip lost grip and accidentally caught his thumb into the ejection port, hitting the outer barrel.
HAZAR! There was movement, the outer barrel moved forwards a few millimeters with the consequence of the shop keeper bruising his thumb. He endured so he knocked the outer barrel through the ejection port and the outer barrel moved forwards freely. A second hit to the back of the slide knocked the slide clean off onto the floor.
Up to now it had been Schrodinger's cat, we didn't know if the gun was operable or not. All the parts were picked up and examined. There was a small chip at the end of the recoil spring and a tiny crack in the rear slide. He wiped down all the part, used his workshop air gun to blow out any residues and quickly oiled the moving parts before putting it all together. With a fresh mag, it fired flawlessly in semi and auto. He took it apart and examined it again then back together, he deemed it fit and worthy for action and didn't even charge me a penny for his hour of struggle and effort.
If you're wondering about the small crack, its in the rear of the slide, on the corner of the where the slide guides the rail of the lower. It's a diagonal crack so if it ever breaks, it'll just be a blunt corner. I've checked over it and fired a few mags through it and everything seems in order. So what was the issue, it was probably me being an idiot when installing the slide to the frame as the outer barrel and inner barrel, hop up did not seat properly, wedging everything together. Lesson learnt: check twice that everything is properly in place before reinstalling.
Thanks again for the help and advice, the quick responses helped me calm down during my first few stressful hours trying to fix it.