All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
If by 'leaving your husband and re-starting a single life' you mean to ask for divorce, then this is forbidden without a valid Islamic reason as the Prophet informed us that if a wife asks her husband to divorce her without a valid reason, Paradise will be forbidden for her, as in the narration reported by Abu Daawood and At-Tirmithi .
If you mean returning to Britain without divorce, then this is also not permissible for the following two reasons:
1- Migrating from a Muslim country in order to reside in a non-Muslim country is forbidden for whoever is not secure about himself from being tempted in his religion, and there is no doubt that if a woman stays by herself in a non-Muslim country there is a danger on her and she is not safe without a husband or a Mahram (i.e. a person whom one is permanently prohibited from marrying due to suckling, marital, or blood relations) to protect her.
2- A wife should reside with her husband and she is not permitted to travel without his permission, and if she does so, she is disobedient to her Lord and to her husband.
Therefore, we advise you to fear Allaah and obey your husband. The reasons which you mentioned, like missing your female friends, your work, and doing Islamic activities in UK, all this is not a valid reason for asking for divorce or travelling without the permission of your husband. On the other hand, if your husband does not provide for you as he should, then in this case you may ask for divorce or go out to work in order to sustain yourself.