Outgoing SMS wrong country code.

Since the last iOS update any outgoing sms messages to typed numbers starting 07 have had +46 prefix (Sweden) added to them rather than +44. The recipient is still getting the messages but the reply comes back with the correct +44 prefix. Any subsequent replies stay in that conversation, but the original +46 conversation remains separate. I have never been to Sweden.

I’ve been in settings ‘country/region’ and reselected UK, but no change. Strangely, when I was updating my own contract address, Sweden was pre-selected as country.

Any ideas?