If something like this was in widespread use it would have much more impact since countries would see whole swathes of the internet immediately go dark when they make stupid laws.
Wouldn't work with somewhere like China, but the UK might still be capable of being shamed.
Best I can find
$ 132,466.01 Africa
$ 4,902,373.13 Asia
$ 49,423,340.29 Europe
$106,546,895.77 N.America
$ 2,509,299.46 Other
$ 6,082,217.76 Oceania
$ 944,844.22 S.AmericaConvert that to GBP and you get about £7.5 million.
Figure that the UK accounts for about 15% of the European economy and assume it contributes to Wikipedia at about an equal share.
That's about £1.125 million in estimated annual recurring contributions from the UK.
You said 10-100/mo, so let's assume £55/mo or £660/year as the mean.
That would be about 1,700 Brits, a surprising number.