Sorry to be late to the discussion here, but the topic of British CVEs is near and dear to my heart.
When there is reference to "twin 20mm" on a British CVE, they are talking about the British Mk V power operated mounts, rather than the hand-operated twin 20 used by the USN. This mount is identified by a slanted operator's station on one side and the two guns offset to the other side.
https://www.shapeways.com/product/D8HSK43ZA/1-56-twin-20mm-oerlikon-powered-mkv-mount-25-ordmThe mount is really visible on the bow in the first photo that DavidP posted -
https://www.navsource.org/archives/03/0302208.jpg. As near as I can tell, when the twins were put in the bow location, they were also mounted around the deck edges, swapping three singles out for two twins. That still left a couple of singles.
Searcher is an odd critter, because she was a member of the earlier "Attacker" class of eleven ships, but she eventually received the weapons upgrades of the later class. The later eleven "Ruler" class were originally configured with eight twin 40mm mounts, while the Attackers started out with only four twin 40s, one on each corner. Again, that photo clearly shows two 40mm mounts forward of the island, so she was updated to have eight twin 40mms. The power operated twin 20s would have been a part of that update also. My guess is that those changes would have happened during a dockyard period in New York between 1 May 44 and 2 July 44.
And like all of the British CVEs, her flight deck was extended before going into British service. A twelve foot extension at the after end is only a whopping 5mm in 1/700 scale, but it is a fun way to differentiate the USN from RN CVEs. There are drawings of the British CVEs, but they were created at the time of handoff from the US yard to the RN, so they don't show the RN changes that were implemented before going into service. I haven't figured out how to tell where the external fuel lines were, as they seem to vary from ship to ship.
And the 4" guns were the US pattern.
I will now stand by for corrections.
Rick
Login
Register
FAQ
I'm really just looking for details to busy up the catwalk area on my Bluejacket Gambier Bay build, and what happens to the lines the run vertically up the sides of the hull. Thanks to BobW"s explanation I have a bit of a better understanding of those. It's a great kit but lacks any details in this area so I'm trying to avoid that sparse look that can happen on some scale model builds, we'll see how successful I am. 
