I do not come from Sheffield, but I did order one of these batteries over a year ago, and it has been in daily use since then. It has proved reliable and problem-free.
As it is fitted to a Mistral, which uses a similar casing but different plugs and outlets in the top lid, it was necessary to extract the cells, fit them in the old Mistral casing, and make a few careful reconnections. That was not too difficult, but it will nullify the warranty. At the time I bought the complete battery the cells were not available on their own.
I would certainly recommend a purchase if the voltage and configuration conform to an existing, but failing battery. The current price is a bargain, especially with lithium prices rising now.