Just got him out of his hutch, and he appears to have removed the scab which had formed. There was also another scab/lump on the injection site, he has also got his of this too and another bit of fur. The sore does look much better now, it doesn't appear to be open and just looks like new skin.
Alex is virtually back to normal now, his fur has grown back on the patches so they can't be seen, can still feel where they were though and I think he still remembers them as he wriggles a lot more now when handled since then.
We got the vet costs covered by Fort Dodge which was good, only £25 but helpful in the current climate.