Walnut,
Unfortunately 'mixed mode' doesn't do much to cure the Low Viz bugbear. It is still a requirement that no aircraft be within the Localizer Sensitive Area for landing clearance to be issued at 2 miles, whether the a/c in front is another arrival (as at LHR) or a departing a/c. During LVPs, the landing rate at LGW is effectively reduced to 12 an hour, down from 25-30 feasable in normal Ops.
This is a funadamental limitation of the current Localizer technology which is basically unsolveable so long as you're transmitting a VHF phased signal. The much-heralded Microwave Landing System (MLS) which may well have solved this problem wasn't taken up because insufficient airports and airlines were prepared to invest in it. I believe the only operational installation in the UK is on 27R at LHR. British Airways did fit the appropriate kit at considerable expense to much of their fleet but unless everyone else has it too and all the procedures are re-written, then the reduced spacing possible in LVPs can't be used.
The future lies with GPS technology, already deployed in several airports in the US, but our regulator is very conservative when it comes to implementation of new technology. We may have to wait for the European satellite constellation to be operational before EASA/UKCAA will accept these approaches.
Meanwhile, we will continue to have disruption to services in extended periods of LVP. Thankfully they are pretty few and far between. Most vis below 600M only lasts for an hour or so. Procedures are in place now, certainly at LGW, to take advantage of even momentary improvements of IRVR above 550M to increase the movement rate.
It's not too many years ago that an airport would come to a halt in LVPs, despite being CATIII equipped as many aircraft/crews weren't. Now practically all a/c are, people are justifiably irritated by delays.
TheOddOne