URGENT. Heating working but no hot water. Piglet John?

[BeYourselfUnlessUCanBeAUnicorn]

We have a saunier duval F30 E boiler. I know they don't make these anymore. From what I can tell it was installed in 2005.

This morning we had hot water. This evening we don't. Heating still comes on. From googling it sounds like it's possible it's the diverter valve.

How much is this likely to cost? Can't get anyone to come out this evening, they are going to phone in the morning, and now I've just remembered our water company is switching of our water until 4pm tomorrow so it will have to be after that.

Don't want to be told it's 100's and hours of work when online says different.

I came on to say "probably diverter valve".

It's just cost us £400 in labour and parts to replace our diverter valve (different boiler), can't remember exact split but a lot of that was parts. Our boiler was installed in 2000, but is a Worcester Bosch so parts are widely available.

Hmm here's my story.

Hot water didn't work, but heating did. Called plumber and he changed the diverted valve.
Then the water worked but not the heating, plumber changed diverter valve AGAIN.
Now the heating works but not the water...plumber called yet again....so it might not be the diverter valve!

We had the same recently, different boiler though. Plumber said probably diverter valve. Cost £200 to diagnose. Got diverter valve off eBay for about £25. Plumber charged £100 to fit it. Didn't work.

DH asked if it could be heat exchanger, plumber insisted no and recommended new boiler. DH decided to tap heat exchanger with a hammer while running boiler full blast, suspecting it was blocked. Voilà, hot water back on. That was about a month ago and no problems since.

Still £325 worse off, though.

That's crap!

Well we still have no hot water. Phoned a company last night. They phoned back to say no one was available so would phone first thing in the morning. Our water was being switched off today though so couldn't have anyone out until after 4. Company said someone would come between 4-6. No one has turned up. Going to just have to phone someone after googling locally. Problem is you never know who you are going to get.

I've had a look around online for a diverter valve for our particular boiler, cheapest is £197! Up to about £250. Not impressed. Only going to call out one who doesn't charge for a call out.