Originally Posted by T. A. Gardner

It is very likely that Britain would have built two more carriers of about the same size as Ark Royal but without two full hanger decks to reach their allowable tonnage under the Washington Naval Treaty. They might also have converted one or two other ships for this purpose instead.
Britain historically built right to the limit of their allowable carrier tonnage. I see no reason they would not have done so in this scenario either. But, much of Britain's carrier tonnage historically was conversions of other vessels to carriers that resulted in the odd polyglot of ships they started WW 2 with. Given financial constraints and the lack of a really strong FAA and good aircraft it is likely that Britain would still try to build carriers on a shoestring rather than turn out properly designed ones.