FWIW, in the UK you can buy a burner phone and SIM in cash without giving away any personal details at most supermarkets (at least Tesco and Sainsbury's). With the new EU regulations removing roaming charges, you can fly to London on holiday, and buy a UK burner phone anonymously with two years of data on it that's enough for heavy Twitter use in all of the EU for £240 + phone cost.

If you're under enough surveillance that your adversary will follow you on holiday and track all your supermarket purchases, you have bigger problems.