I'm surprised some people here seem to know for fact that the F35 will replace the Typhoon.
Follow up orders , if at all in originally planned numbers, will only be decided at SDSR2015.
Also drop2 T1 typhoon upgrades are ongoing with drop 3 upgrades already in the testphase and drop 4 is already in the planning stage, meaning the 2019 planned T1 retirement is no longer a fact.
The first F35A's will eventually replace the Tornado's ,which are currently getting their final upgrades, and only the oldest Typhoons will be replaced by the F35 if they get them in sufficient numbers.
Typhoon is here to stay till at least the middle of the century and in all lkelyhood in larger numbers than the UK's F35A+B.
Also, speaking of the twinseater issue, I've read an interesting piece explaining that in the future twinseaters might proove to be a big asset, certainly when hybrid UCAV-manned-AC operations are more common.
The F35 just has no place and weightmarging to make a twinseater likely.
There has been very little relevant news lately concerning the F35, which seems to have taken the focus of the whole F35 saga for now but besides some vague longterm commitements there also has been little good news about the F35, for many nations, it still is by no means a reasonable follow up for the platforms it was envisioned to replace at its conception.