Thank's Drew,
Unfortunately I would need help to set up a VPN account. Until sometime in the last twelve months Shetland phone/internet access went via a microwave link from Caithness piggybacked over Orkney. 3MB was described as fast broadband. Anything that slowed access even more would have just increased the frequency of timed out messages.
We travel round rural areas of the UK on a regular basis. The purchase of a cellular enabled freed me from needing to find accessible Wi-Fi. BT list one hotspot near the 30 plus miles of the A897. Plus I don't think it's near enough to to road to be accessible anyway.
I am not sure how the Ordnance Survey Mapfinder would work away from Wi-Fi. I don't know how it does it because the iPad does not have GPS . But even with the iPad's Wi-Fi and cellular turned off Mapfinder is still able to is able to more or less able to find your current location. I have only tried this in urban areas that have been Wi-Fi/mobile signal rich. Unless anyone knows any different I see this as an indication that it may work in the Isle of Man. ( I have downloaded two 1:500,000 Isle of Man map tiles. I have just looked, all the other IoM tiles are currently listed in Purchase as unavailable. )
I have stared using OS Mapfinder 1:250,000 maps in place of the paper versions. They don't take up any physical space, don't weigh anything & are more manageable than paper in windy conditions. But don't expect the maps to be up to date. I downloaded the tile covering Vidlin, Shetland in the last few months. Amongst other out of date info it still shows a post office. Herculson's ceased being a post office at least five years ago in a round of rationalisation.