Will my UK SIM card (O2, EE, Vodafone) allow free roaming in Gibraltar, or is CheapESIM a better value?

Unfortunately, no. This is another significant roaming pitfall. While Gibraltar is a British Overseas Territory, it is explicitly excluded from the free roaming zones of most UK carriers, especially post-Brexit. Expect to be charged expensive 'Day Pass' rates, often £5-£10 per day, by providers like O2, EE, or Vodafone. CheapESIM provides a far more cost-effective alternative with transparent, fixed-price data plans for Gibraltar, ensuring you avoid these hidden daily charges and get more data for your money.