Why did the aircraft need to fly around to burn off fuel, would it have been too heavy to have landed at EGCC otherwise? At least he got to book another hour in the logbook
The 757 (take note BBC!) does not have a fuel dump system. They have various weight limits depending on the model but a typical MTOM is 113 tonnes and MLM 90 tonnes. you can, in an emergency, land at anything up to MTOM, but that requires an 'overwieight landing' engineering check afterwards which would take the aircraft off the line for some time, so its not somethign you want to do unless you have to (on fire, smoke in cabin etc). However as this aircraft is gonna need to go in the shed for a new engine anyway I can't see that as a consideration.
For a flight to Lanzarote a typical actual TOM would be 95 - 100 tonnes. so not too much to burn down to Max Landing Mass.