The Brompton I bought from eBay was in good condition overall, but it had a cracked mudguard at the front.
My guess is that it was caused by someone folding the bike poorly and, while it was not causing any obvious problems, it didn't look good, and it annoyed me.
So I fixed it.
The longest part of the job was waiting for the part to arrive, since it was seemingly held hostage by Hermes for a couple of weeks.
It arrived today, and it took about 10 minutes to remove the old mudguard and fit the new one. It was much easier than replacing the rear mudguard as part of the addition of the rack, which entailed removing the rear wheel.
So that is, I think, the last job I "need" to do. What I really need to do now is build up my stamina when actually cycling the thing, as some of the hills around here — steep, but short — are challenging me at the moment.
Although a telescopic seat post is still tempting me. Aaargh.