Blue bubble is messages you sent via iMessage.
All incoming messages are grey, regardless of whether they were sent to you via SMS or iMessage.
I don't know of any UK plan that charges.
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My father doesn't and so pays PAYG rates when he uses his. Which probably makes sense for him, given his infrequent use pattern.
Blue bubble is messages you sent via iMessage.
All incoming messages are grey, regardless of whether they were sent to you via SMS or iMessage.