Ignition barrel breaking up/failing?

A while back my key was stiff to get into ignition barrel and took a bit of a wiggle, so I used a bit of GT85 In it which is similar to WD40 (turns out it was the wrong thing to use) but since the key has been fine asides from the steering lock rarely engages with the key out and also I'm sure there was a flap which sprung back when key is removed which now doesn't . I tried to get steering lock to engage when I got home from work this evening but found I couldn't get the key back in and it appeared that something within the barrel just inside had become dislodged and was stopping the key going in. After a few minutes I managed to remove it and then the key went I fine but now I'm a bit concerned that A it'll happen again and I might end up stranded and B perhaps an unreliable steering lock is a potentially more dangerous than I first thought. Anyone had similar issues? I don't really want to change the ignition and lock barrels if I can avoid it.

Changing the barrel out isn't that hard.  Using your old wafers will keep your current key.  
You will remove the new wafers, and insert yours in one at a time so you can't get them in the wrong spot.

IIRC you can order a new Upper Bearing Assy
https://www.heritagepartscentre.com/uk/155905851-steering-lock.html

Then order a new ignition switch, and barrel assembly then you can take your old one out, rekey the new to the old and be good to go for another 30+ years.

I'm not sure I'd need the lock assembly, as I think the lock only working some of the time could be due to whatever I did to the ignition barrel when I cleaned it up, I could be wrong though. I was looking at my key when it happened and it is fairly worn out so that may not be helping. My biggest concern is the bit of metal that appeared to be floating around when I took the key out, I moved it and managed to get the key working again but don't really want to get stranded anywhere.

How do you change a wafer? I was assuming I'd have to do all the locks tbh

you are putting your tumblers into a new barrel unless the piece you found was one of the tumblers

I'd imagine that if it was a tumbler (I'm assuming tumbler and wafer are the same thing?) then it would be unlikely I'd move it out of the way into a place where then the key works? I don't know, i know nothing about locks really I'm just making a bit of a guess