You missed out Northern Ireland and Great Western and I have both Warwickshire & Northants & Derbyshire, Leicestershire & Rutland coming under the TAAS (The Air Ambulance Service) umbrella.
Open to clarification, but my understanding as follows:
Cornwall AA - AW169 (G-CRWL)
Devon AA - 2 x EC135-P2+ & 1 x EC145-T2 (G-DAAN, G-DVAA & G-DAAS)
Dorset & Somerset AA - AW169 (G-DSAA)
East Anglian AA - 2 x EC145-T2 (G-RESU & G-HEMC)
Essex & Herts AA 1 X MD902 & 1 x AW169 (G-EHEM & G-HHEM)
Great North AA - 3 x AS365N2 (1 x Spare) & 1 x AS365N3+ - (G-NHAA, G-NHAB, G-NHAC & G-NHAD)
Great Western AA - EC135-T2+ - (G-GWAC)
Hants & Isle of White AA EC135-T3 (G-HIOW)
Kent, Surrey, & Sussex AA 1 x MD902 (Spare) & 2 x AW169 (G-KSSA, G-KSSC & G-KSST)
Lincs and Notts AA - AW169 (G-LNAC)
London AA 2 x MD902 (1 Spare) (G-LNDN & G-EHMS)
MAGPAS AA - AW169 (G-MGPS)
Midlands AA 2 x EC135-T2/EC135-T2+ & 1 x EC145-T2 (G-OMAA, G-HWAA & G-RMAA)
North West AA - 3 x EC135-T2 (G-NWAA, G-NWAE, & G-NWEM)
Northern Ireland AA - 2 x EC135-T2 & EC135-T2+ - (G-NHEM & G-NIHM)
Scotlands Charity AA 2 x EC135-T2+ - (G-EMAA & G-SCAA)
Scottish AA - 2 x EC145-T2 (G-ISAS & G-GSAS)
Thames Valley AA EC135-T3 (G-TVAL)
The Air Ambulance Service (TAAS) - 2 x AW109SP (G-HEMZ & G-TAAS)
The Childrens Air Ambulance (TCAA Not HEMS) 2 x AW169 (G-PICU & G-TCAA)
Wales AA - 3 x EC145-T2 (G-WENU, G-WOBR & G-WROL)
Wiltshire AA - Bell 429 (G-WLTS)
Yorkshire AA - 2 x EC145-T2 (G-YAAC & G-YOAA)