i have done quite a few diversions over the years, some were long, others short but interesting, i have listed some of them below:
-Sleeper diverted via ECML, via Primrose Hill Station and other route,
-Glasgow-Kilmarnock-Dumfries-Carlisle-Settle-Manchester-Crewe on Virgin Voyager,
-Via Bescot diversions when Trent Valley shut,
-Birmingham-Walsall-suttton Park-Coleshill-Whitacre Junction then Tamworth normal route,
-Birmingham-Shelly Oak-Lifford curve -Camp Hill-Nuneaton etc on Cl 31 diverted East Anglia service,
Man Pic-Salford Central-Man vic-Heiden Bridge- via Huddersfield or straight on to Leeds overnight TPE service,
Birmingham-Oxford-Foxhalll Curve-Swindon-Bristol,
Exeter-Honiton-Yeovil-Castle Cary,
Waterloo-Basingstoke-Salisbury-Westbury then normal route, non stop Andover and Salisbury,
There are other diversions I have done, which cant remember right now, some including freight only lines and curves.