Well it is at the back of the tank behind pipes so might be difficult to get to. Last time I saw the electrician he said I would have to have a new fuse box, only had it a few years ago, as it is not certified under the new European rules and it was going to cost a few hundred pounds, so am loathe to have to call him out. Could a plumber not do it, as I have a few other things I need doing.
Yes a plumber could do it quite easily however he will need basic continuity testers to determine if its the stat or element...ask before you call him out.
If its hidden behind the tank then you may need to take the tank out!!