Sounds like the best solution
I didn't get around to picking it up before the break.
However, we were in Ikea today, and I discovered that they've got this thing called "Circular Hub" where they buy back (and resell) second-hand, ex-display, etc., Ikea furniture.
They had exactly the same desk I'd seen on Gumtree, so we grabbed it. It was a little bit more expensive, but it saved the effort of driving into (and parking in) Hammersmith.
So, anyway, once the garden's dried up a bit after the last few days' rain, that'll come out of the car and into the office.