The F-35s will become operational at around the time when the Tornados will be gone. Only 48 aircraft have been comitted to, out of an original 138 planned. There has been talk in the past of possible A model F-35s being ordered after the initial 48B to replace Typhoons. That, apparently, is to be discussed in the 2015 SDSR.
Up to 138 seems much but between the 2 number again possible, ofc A after the 48 first less expensive mainly but delivered 2025/2030 later.
Actually :
160 Typhoon ordered : 53 Tr 1, 67 Tr 2 and 40 Tr 3.
In service 124 Typhoon, 102 Tornado, one Frontline Typhoon sqn get 13 fighters, Tornado 16, in more 1 OCU for each and a OEU for the 2 i think about 20 fighers by OCU and 10 in OEU.
According it a forward fleet of max 80 Typhoon : 4 x 13 + 20 + 5.
Tornado : 3 x 16 + 20 + 5 : 73.
In fact very few based on the total mainly for Typhon, very strange, i don' t know RAF do with its fighters ?
Can easy get in more 2 squ, which are in more small, all main Western AF have sqn of 15/24 aircrafts.
With 220 fighters bombers RAF get only 7 " small" combat sqn !!!
For comparison In France we have 95 AF Rafale, 77 in the forward fleet : 3 x 20 + OCU 5 + OEU 5 + 6 flight/small sqn to UAE big difference !