Inside the house it's customer demand that drives improvement, with mobile data blackspots causing subscribers to switch provider.
On trains mobile operators can't improve coverage on their own so the Government is stepping in to help.
Better outside than in
The big four mobile networks - EE, O2, Three and Vodafone - are committed to 90% coverage of the UK by 2017 based on geographical terms.
Their coverage of the country isn't uniform, however, and some areas have better statistics than others, with the rural blackspots typically grabbing the headlines.
But it's not just the geographic area that people live in that determines how good or bad coverage is - it's also whether they are at home or out and about.
As more and more people prefer the mobile phone to their landline indoors, GSW have researched how good mobile phone coverage is inside our homes.
And the result showed that, as GWS chief Paul Carter put it, mobile operators are struggling with "the brave new world of in-home mobility".
Almost one in three people say they "regularly" have issues making and receiving mobile calls from home, 40% have a black spot in their home where they struggle to make and receive calls, and 30% regularly suffer mobile internet connectivity issues.
GWS also found that some mobile phone providers performed significantly worse at home than others, with EE and Three being prime offenders.
One in 14 calls made at home using EE's network failed. One in 20 such calls using Three failed. Compare that with just one in 100 failing when using O2 or Vodafone.
Tests also showed that all of the big four UK operators experienced problems extending their 4G/LTE networks into British homes.
Three's 4G network enjoys 78% coverage outside properties, compared to 55% inside. EE's 4G network offered almost 100% coverage outdoors - but only 85% when tested indoors.
Vodafone had 87% 4G coverage indoors; O2 achieved the highest in-home 4G penetration with 90%.
Difficulties with extending networks into the home also affected mobile data speeds. Uploading pictures took significantly longer inside than out.
EE's mobile data network delivered the fastest average throughputs during GWS' in-home testing programme, although their speed advantage is unlikely to make a difference to most customers' mobile internet experience.
Train services could be better
It isn't just the home where mobile phone coverage can be intermittent. We all understand that poor reception on trains is something of a given, with numerous reasons for a patchy service.
One is commercial, because mobile operators don't prioritise masts to be near railway lines. Instead they prefer them placed near well populated areas.
However lost calls and intermittent internet access are also caused by physical barriers to radio signals, like tunnels and trackside clutter; carriage walls and windows also weaken signals.
GWS showed just how poor reception can be in a connectivity study carried out in October last year, where almost a third of mobile internet tasks attempted failed.
On the 10 most popular commuting routes in and out of London, an average of almost one in four 3G data packets and more than one in three 4G data packets didn't make it to their intended destinations, and one in seven voice calls failed.
There was a difference in performance depending on whether the train was at a standstill or moving, and what speed the train was travelling.
One in four data failures occurred on trains in stations, compared to a fifth on open track; a quarter of call failures occurred in stations, compared to a third on open track. Failures are most likely to occur when a train is travelling above 50 mph.
The tests showed that Vodafone gave the best 3G data service and was the most reliable at getting data packets through. It was also the fastest, giving an average of 2Mb during testing.
EE gave the best 4G data service while being as reliable as Vodafone, but was faster with an average 5.6Mb. Three appeared to be the best network for voice calls.
We're getting there
Coverage is slowly improving in areas that were performing badly.
In remote rural areas the Government is committed to improving broadband.
In the home, Paul Carter says customer expectations have risen, so data performance must be turned into "a selling point, rather than a liability" - otherwise customers will switch to another provider.
And on trains the Government is addressing concerns by investing millions of pounds to equip trains with new wi-fi equipment.
There are still areas that miss out on broadband and mobile coverage. But whether it's through competing with one another for customers, or with a little help from the Government, mobile providers are moving towards providing complete coverage everywhere.
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