Jersey is a tax haven (40% of the economy is evading tax), lying 20km from France and 160km from Britain, so there's no reason the internet access has to be bad.
Citation needed. You are welcome to pay maximum taxes where you live if you like, but jurisdictions with lower tax rates keep the pressure on governments to deliver a good return on investment to their citizens. When I moved from San Diego to Dallas after the dotcom bust I slashed my taxes which was great (no income tax in TX). This wasn't tax evasion, it was common sense. San Diego was no longer a good investment.
Also, you totally missed the Gigabit fiber-optic broadband plans[0]. I have a 1GB unlimited plan from their competitor for £55/month[1]. Standard fair use clause applies but I've never been throttled and I use massive amounts of data every month.
http://www.jtglobal.com/Jersey/Personal/Broadband/Products/H... — it's a bit expensive, and has a usage cap, but that seems more to do with the lack of competition than it being an island.