Thanks both,
Normally I’m much more sanguine about sharing our property with the local wildlife, but unfortunately my wife is allergic to wasp stings - in a potentially ‘go straight to hospital, do not pass go’ kind of way - so the little blighters had to go, especially as they had taken up residence directly under our back room windows.
Anyway, I ended up using Mark from Combat Pest Control ( http://www.combatpestcontrol.com/pest-control/south-east-london ), purely because I happened to bump into him on Saturday while he was finishing up a similar job for one of our neighbours, and he was able to pop round immediately.
He seemed knowledgeable, very courteous and did a good job (as far as I can tell). Turns out the company specialises in giving jobs to ex-servicemen, and gives back some of the proceeds to military charities. All a big thumbs up from me!