About the format
Developed by Sony, Beta (more often referred to as Betamax in the UK), was the first home video recording system to launch in the UK in the mid-1970s, but which ultimately lost the famous "format wars" to VHS.
Despite solid initial sales, by the mid 1980s its market share had dwindled to about 7.5%, and Sony themselves gave in to the inevitable and started making VHS machines in 1988. Although Betamax machines were produced until 2002, and tapes until 2016, the format was pretty much dead by the early 1990s.
There's a common myth that the "wrong" format lost out, as the quality of VHS was actually worse than Betamax. It's not that simple however. There were a whole series of mistakes made primarily by Sony, from short recording times, lack of in-built timers and high licensing costs that contributed to its downfall. Also, in reality the supposed quality of Betamax over VHS comes from the very early NTSC models that recorded at such a fast (therefore higher quality) speed that tapes didn't even hold enough tape for an hour. By the time the PAL models were introduced to the UK, the recording speed had been cut in half to increase the maximum recording time, and any perceptable quality over VHS was effectively gone.
Note that we are talking about the home Betamax format here, and not the later confusingly named professional formats such as Betacam. Although the tapes can sometimes both look similar and actually be interchangable, the recording formats are completely incompatible.
Recording Time
Tape length in the UK can be anywhere from 32 minutes on an L-125 cassette, to about 216 minutes on an L-830*.
Fun Fact: the naming scheme reflects the length of tape in the cassette in feet. Spectacularly unhelpful for the consumer, unless you happen to know the number of feet per second at which your machine records! Compare this to VHS tapes which show the maximum recording time in munutes. Much more sensible.
*Some NTSC (USA) decks could reach 5 hours on a cassette with βIII mode - probably to allow recording of American Football matches - but that's not a thing on UK decks. Honestly, this a bit of a rabbit-hole, so let's stick with just over 3 hours for UK tapes.