It's more of a case of comparative costs. Invariably improving productivity means expenditure and less people needed. A drive in both set ups will be trying to increase market size so assuming productivity will do anything about that is not correct.I suspect it's more the other way around. Low productivity encourages low wages.
A daft example a pie maker shown on the TV. A number of people walking around with trays of pies doing various things to them. Not very efficient but he meets his market size. If say Puka pies has a factory they would have far more capital invested to meet demand. Rather difficult for the laborious method to match and probably no point in trying. He could try a production line pproach but different operations may need differing numbers of people - more complications and it would need to fit in with his premisses. I though no it wouldn't and not even worth doing.
Maybe in your terms expand your UK aspect by taking on more people - would you be able to find business for all of them? Would you like an excess capacity allowing some to not do much at times at the same pay? Sure you may want some of that but how much?
This is why there is an interest in billioners and hedge funds etc. Large businesses are needed They cost billions.