Land Forts
AA
Radar
Airbase
All that can be build by UK and be placed in France, so France has only to repair them.
Infrastructure in front line provinces
More important is the infra between Paris and the designated front line. Donnot forget to build an ESE-highway to Dunkerque for the UK!
Imo France should build lots of Infra and some factories. Later France should build some Int and many Inf-SpArt to utilze the tc of France. The UK should mobilize its manpower into motorized or even mechanized divisions in order to utilize the higher tc of the UK. The UK should also build Infra as it has many provinces deserving better Infra. And the UK should build many Int or MRF. If the UK has abundant ic it may start to build up a bomber force or a navy.