It must have been a traumatic time for many Midland Red folk when they were hornswoggled into the PTE. After all they had been part of a company that had good mottoes - 'All Over The Midlands' (which they were) and 'The Friendly Midland Red'. The first one obviously disappeared as it became only part of the Midlands now. As for the second only Red staff can answer that.
The childish name 'wumpty' was probably chosen by an officials child over breakfast one day.
When is was at Great Malvern, when in the RAF, one of the civilian people asked me what I was doing collecting fares on a a local Midland Red bus service in Great Malvern. They were puzzled as RAF personnel usually did not have secondary jobs - especially given the type of work that was done at Malvern. I commented that it must be a double!