I would smash off to gain access to extend and insulate and chase a few inches. Looks easy enough to get a filling knife with some bonding plaster. Tight but can be done.
Dont understand how price can be discussed on a technical site. Who is to say what one electricians costs and overheads are against another. Who knows what make of parts were fitted and the discussions with the landlord at the time. How long did it take to find the fault and then fix. Why is the...