There are a couple of other cases where SVFR could be useful.
VFR does not exist at night in controlled airspace in the UK so if you have a night rating and the viz is 10k or more SVFR is your only option.
Through a control zone with a low cloudbase you could still have 10K viz but if VFR you would need to obey the 1,000 foot rule, however SVFR you could undertake the transit without, although of course you would still need to land clear.
As mentioned the BUR LHR clearance is always SVFR and usually not above 1,000 feet under the inbounds or departing.