Gerry Fiennes, well-known railway author, and also General Manager Eastern Region in the 1960s, was also a daily regular on the loco-hauled service, as he lived in Southwold, from where he commuted daily to Liverpool Street, class 37 hauled (he would have known them as EE Type 3).
The original dmus from the 1950s were indeed the pioneer "Yellow Diamond" Met-Cam and Derby units, based at Norwich. Before them, there was quite a mainstream through service from Liverpool Street through to Lowestoft and onward on the now-closed line to Yarmouth, hauled by Britannia Pacifics.
The Wickham dmus described above were based at Cambridge rather than Norwich, so would have not been common on the line. Built by Wickham at Ware in Hertfordshire, on GE territory, the five two-car units had completely standard "Blue Square" mechanical parts and controls, but the Wickham-built bodies were to their own design. When withdrawn as "non-standard", after a good 10 years service, and ostensibly by command from the BR HQ at Marylebone who didn't realise how well regarded they were in their area, three of the five were sold back to Wickham to fill an export order they had from Trinidad, while Fiennes himself took a fourth and converted it to a two-car General Manager's Saloon, which was used on the Eastern Region for many years afterwards. Fiennes himself wrote how commercially useful it was to bring it to important meetings with major freight customers, local politicians, etc, and it was a lot more economical than a Class 47 and saloon coach, used before and after. When not in use for the bigwigs it was a useful unit for route learning, line inspections, and such like. The Wickhams had a notably attractive interior design.
As I recall, Anglia's DMU's were all of the low density variety. I don't think any high density suburban units got that far out?
The 20 unique Derby high-powered "Orange Star" 952hp 3-car suburban dmus were initially allocated to Stratford, and although designated for the Lea Valley line from Liverpool Street through Tottenham Hale etc, which was not electrified until about 1970, they got used on Stratford's rural branches as well, St Margarets to Buntingford (now closed) and Wickford to Southminster. They may well have got onto the East Suffolk on the weekend summer excursions from GE suburban stations, a type of traffic long gone. After 1970 these cars were all transferred over to Finsbury Park to remove many of the remaining loco-hauled inner suburban services from Kings Cross, before electrification there.