https://www.britishswimming.org/browse-sport/swimming/officials/officials-qualifications-training/

The club will reimburse any fees onces the training is completed.

You can start off as just timekeeping or start L1 training which includes timekeeping. If you were to get all the online theory completed over the summer you would be well placed to complete your practical signs offs from any of the September comps onwards.

The South West Region also provide a funded L1 course: https://www.swimwest.org.uk/file/enrolling-on-the-j1online-sesw-region-2-2.pdf