Yes, it was essentially a "hopped up" Spitfire L.F. V navalised for CV ops, but it wasn't a "conversion", it was built as a naval fighter from the outset, albeit from a land based design.
They had a lot of accidents in the Torch operation because of the low wind conditions and the small CVE decks many operated from. They had a much better landing record on the larger Fleet Carriers in the pacific.
I think they continued on with it because it was being produced, and they probably needed the #s to fill out the Fleet. The RN built up a large Carrier force by 1944. Im also not certain if the RN had trouble getting enough F4Us and F6Fs from the USA. There were a lot of issues there. National pride might also be a factor?, but I can't say for certain, im only speculating.
"Eh didnt the Commonwealth countries produced bombers and fighters for RAF?"
Yes, many. Mostly from Canada.