Was this called Beggarman, Thief in the UK?

No...

'Beggarman, Thief' is the title given to Irwin Shaw's published novel which is the sequel to the original novel of 'Rich Man, Poor Man'. 'Beggarman, Thief' came out after Universal Television had already made 'Rich Man, Poor Man: Book II' which wasn't based on any book. However, a two-part TV movie adaptation was made of the 'Beggarman, Thief' novel but it didn't bear any solid relation to the original mini-series or its sequel.