TCB = Topcashback
What does "apply via TCB" mean?
Indeed. I have few Three SIM cards with free 200MB data monthly and never ever topped them up for 3 years :) Handy to use abroad on my tablets.
I've been with this network for 2 years now and I am very pleased with it. You can set up automatic topup via paypal so you don't have to worry about anything. It'll automatically topup below £2 credit or every 4 months for £10 whichever comes first. Its an MVNO that use the EE network, so you get pretty great signal. The online panel is great and being able to make sure the nana doesn't accidentally use a premium rate number via a block is great. Your credit never expires btw.
Probably best going for O2 top up £10 for 321 tariff. 1p mb 2p text 3p min calls Same for 3 three network No need to top up every 4 months. £10 could last you a year or more. If you use more then probably for a £5-6 monthly tariff maybe Plusnet or ID mobile