TM
Almost correct, only the 200 series are older than Coastal Command. They were originally RNAS sqns which were renumbered by adding the 2 in front ie 1 Sqn RNAS became 201 Sqn RAF and 2 Sqn became 202 etc, etc.
:Anorak On:
According to Jefford's book "RAF Squadrons" 1 - 200 were RFC/RAF Squadrons; 201 - 299 were ex RNAS; 300 - 309 were Polish sqns; 310 - 313 Czech; 315 - 318 Polish; 320 - 322 Dutch; 326 - 329 French; 330 - 334 Norwegian; 335 - 336 Greek; 340 - 347 French; 349 - 350 Belgian; 353 - 399 RAF; 400 - 445 Canadian; 450 - 467 Australian; 485 - 460 NZ; 500 - 509 Special Reserve/RAuxAF; 510 - 599 RAF; 600 - 616 RAuxAF; 617 - 650 RAF; 651 - 673 Army associated; 674 - 699 RAF.
:Anorak Off:
Edited to add: I believe that the 700 and 800 series were all Fleet Air Arm and according to the RAFHT 900 series were Aux AF Balloon Sqns
A lot of the badges can be seen
here