The hybrids I fondly remember...
4 EPBs with a mix of BR Standard and SR style coaches
4 x 4 EPBs with 9 compartment trailers (instead of 10) that were built in the 1940s as composites but never ran as such)
During the EPB facelifting programme, a mix of BR blue and blue/grey formations shortly before being sent to works
Seeing one or two 3-car Class 455s running in public service whilst coaches were away for accident damage (I believe there were 2, or more units temporarily renumbered "5800")
The former Southern Region were very good at "cut and shut" on accident-damaged coaches where for example, I saw first-hand, in BR workshops (e.g. Slade Green, Eastleigh or Selhurst) 4 Cig driving cabs being welded onto 4 Vep driving coaches (or vice versa) to replace native damaged cabs. Once painted up; you could never tell...
There was a 4 Vep running around in Connex livery with a former 4 TC driving trailer (unit 3582 ?)