And a little explanation from OFCOM's FAQ's if you can't find your mobile opererator listed . . .

The map shows the coverage of the four main network operators in the UK: EE,Vodafone,O2 and Three. All other mobile operators in the UK provide their services over these networks. Examples include:

Virgin Mobile, Asda Mobile and BT Mobile use the EE network.
Tesco Mobile and Lycamobile use the O2 network.

Thanks for this Humphrey. Looks like I've planned a no signal route most of the way - even on Vodaphone!

That's not a bad idea peace and quite

That's useful info - thanks HMP3.

Take care though - the coverage shown may not be as great as the map would have you believe. Not because the signal is not there, but because many modern phones need up to 10 times the signal strength of the old "dumb" phones of ten years ago. The battery life of modern "smart" phones is pretty woeful - hence the plethora of outdoors oriented charging devices of varying effectiveness.

As far as the manufacturers are concerned this doesn't matter, because most buyers of smartphones:

a) use it for accessing the internet rather than making voice calls and sending texts

b) generally have access to recharging points either in cars, trains or office/home

c) live and work in urban/suburban areas where signal strength and 4G reception isn't a problem.

So as far as they are concerned, degraded voice/text performance is unimportant. As long as their customers can check on their Facebook status, take pictures or order a pizza, that's fine. Unfortunately, that doesn't help much when you need to make an urgent call on a windswept rain soaked hill in the highlands.

So, that the old Nokia that you've got shoved in a drawer somewhere might be a better bet - or at least a re-assuring backup for your all singing and dancing gps enabled routebuddy routing internet surfing smartphone.

Interestingly, ofcom are onto this too.

If you have an old "dumb" phone, it might be interesting to take it out with you and compare voice signal performance with your "smart" phone where the signal is marginal. And compare the battery life - you could be very surprised.

Fully agree, Phil, that's why I sold my fancy smartphone and went back to a simple Nokia (c £13 in Tesco). The other great advantage is that it doesn't need recharging for the whole crossing. I do switch it off when I'm in no reception areas and at night, but don't have to worry about charging at all.