"Free" mobile phone

Good morning
I have a mobile phone purchased in France on the Free network (we use them for our TV, internet and fixed phone line). I am popping back to the UK for a week so my question is whether I can use my French phone in the UK or should I just stick to my UK one. I don’t want to incur huge phone bills.
Thanks in advance.

If I use my French SFR mobile in UK to phone UK numbers - it costs me. But that is in my SFR contract.

You might be best to check out your own France Free contract…

Thanks Stella, I’ll try and speak to them before we cross the Channel.