Right, time to let you all off the hook............
1/ Texan = Harvard
2/ Washington = B-29 Superfortress in RAF service.
3/ Bolingbroke = Canadian Blenheim
4/ Bisley = Blenheim Mk.V (only used for a short time)
5/ Canso = Canadian Catalina
6/ Nighthawk = P-70 nightfighter variant of the A-20 Havoc.
7/ Banshee = A-24 - USAAF version of the Dauntless
8/ Thunderbolt = The original name for the METEOR changed to avoid confusion with P-47 in March 1942.
9/ Martlet = FAA name for the Wildcat, standardised back to Wildcat in Jan. 1944.
10/ Gannet = FAA name for Hellcat, changed back Jan. '44.
11/ Tarpon = FAA name for Avenger, changed back Jan. '44.
12/ Hereford = Hampden with Napier Dagger engines (100 built), most converted into Hampdens after re-engine with Bristol Pegasus.
13/ Lexington = USAAF version of the Ventura.
14/ Apache = USAAF name for Allison engined P-51A.
15/ Seaford = Sunderland MK.IV .
16/ Kaydet = USAAF name for the Boeing-Stearman Kaydet, which most people just call the Stearman.
17/ Digby = RCAF name for the B-18 Bolo.
18/ Nomad = PBN-1 - US Naval Aircraft Factory built Catalina, had a slightly different hull design and introduced the tall tail, of the 156 built 138 went to Russia.
19/ Skytrain = USAAF name for C-47, Dakota was RAF name.
20/ Gosling = Royal Navy name for Grumman Widgeon.
21/ Convoy = Original RCAF name for the Catalina, changed to Canso to avoid confusion with ship convoys.
22/ Tess = Allied name given to Japanese built DC-2 used by Japanese military in the Pacific.
23/ Tabby = Allied name given to Japanese built DC-3 used by Japanese military in the Pacific.
24/ GST = Russian built Catalina.
25/ Skytrooper = USAAF for C-53, basically the same as the C-47 except that it has no freight door.
26/ Express = C-87 transport version of the B-24 Liberator.
27/ Spider Crab = Initial name for the DH Vampire.
Not bad, between you you got 21/27.
I guess I will have to try harder next time