Hack bike hadn't been cleaned or maintained for ~10 years, so I cleaned everything down. Rear mech had been overthrowing and clattering on the spokes in the 25T sprocket, so I'd been limited to 39x23 when riding with my 3yo in the Hamax seat - not ideal for getting up steep Staffordshire hills! Adjustment screws had turned to cheese and rear mech was generally knackered, so I installed a new 9spd Sora medium cage mech which works okay. 9spd cassette had been 12-25, but I wanted something a bit smaller, so I dug out a 28T and a spacer from the box-o-bits, took off the 12T, and swapped the 13T sprocket for a top-sprocket version. It's a bit of a mish-mash, but it runs without jumping, and indexes fine now. I feel like I could ride up the side of a house in 39x28 - I've never had such a small gear on a road bike!
Fitted some Vredestein Fortezza Tricomp tyres - I hope they're as nice to ride on as when I last had some, 20 years ago - and a new stem, because my old one was a MTB stem, bodged to work with road bars (I know, I know...)