Is he an expert or am I hoping he'll live up to his name.
Just over 30 years experience before I retired.
I just looked on the council web site and they charge £80 for domestic problems.
That's not a bad price, assuming its for 3 visits, do a web search for a local independent, he might be cheaper, but also look for a profession accreditation.
BPCA is the industry standard.
I'm also worried about where it is finding water.
Its either going out for water or licking condensation off your water tank.
One size never fits all, and this time of year it could be a squirrel with a nest.
Check the droppings they are quite different.
Professional 3rd generation Anticoagulant baits are 10x stronger than anything you can buy from the likes of B&Q etc.
These also make the target thirsty, and 99 times, they'll go outside and die, ( looking for water) they also desiccate the target, and there is very little smell, the smell comes from the live, rat having scent marked its territory.
Having said that of course if you are unlucky and it dies inside, they do smell bad for about a week.
Get some proper deodoriser, and put that around the place, on cotton wool type pads, not not only masks the smell, but also attracts it.
It in itself smells a little like disinfectant, its quite strong but not that unpleasant in its self.
Just throw the pads away after about a week.
If you have thick insulation, its running under that, and that's where you put the poison or indeed snap traps,
buy the old fashion ones, not the modern "crocodile" type.
A fen MkIV is even better, but learn how to use them, they break fingers. Bait this with a smear of jam or peanut butter on the tread plate.
The other alternative is a "live cage trap" baited with mixed fruit and or nuts Salted (KP type) peanuts work best.
From ground level I can see no obvious point of entry.
They will tunnel underground some distance away, and go up the cavity wall.
Do you have tall trees within 8 feet of your house, squirrels will jump this distance and go under your roof tiles.
Do you have a trellis or some type of "climbing plant" on your house?
Both rats and squirrels will climb this.
Is your rain pipe close to the wall? I've seen rats climb a wall with their backs to the pipe, wedging themselves against the pipe,
and then getting under the roof tiles.
I can't really offer a specific solution without actually investigating it first hand,
But hopefully that is all food for thought...