OP if you want to know they are financial backers of the Labour party and also share your information with an organisation called
Mass 1 , who are a marketing voting and polling company who also have close links to the Labour party.
The owner of the network is believed to be involved in political campaigning against certain political parties and was accused of "aiding a dirty tricks campaigns during industrial disputes", including giving free calls and texts to strike committees and encouraging political union activities. They will use your data for quote "
research, surveying, polling, general campaigning, and engaging with you, including sending you messages (email or SMS) for these purposes on our, or a third party's behalf". They will process your data trying to anonymize it, but using it for research purposes, and you agree to this in the
terms.
If you give permission *(which you may do by default. as agreeing to the terms is probably a mandatory checkbox) they will also sell your information to 3rd parties for marketing purposes.
In terms of it's viability in the long term In the year ending December 2013, TPO reported a loss of £1.54m on £62,227 of revenue, the year before it printed revenue of £456, resulting in a £566,231 loss.
Other MVNOs have gone out of business and left customers with no service and no refunds on credit, so the choice is yours given the information above.