If the majority of the leaseholders want to buy the freehold, the freeholder can't refuse. If they don't want to sell then you might have to go to arbitration.
IMO there isn't much point extending the lease if you're going to buy the freehold in the future - running the lease past 90 years would only cause a very slight depreciation in the valuation of the property and you aren't looking to sell.
If the majority of the leaseholders want to buy the freehold, the freeholder can't refuse. If they don't want to sell then you might have to go to arbitration.
IMO there isn't much point extending the lease if you're going to buy the freehold in the future - running the lease past 90 years would only cause a very slight depreciation in the valuation of the property and you aren't looking to sell.