Thank you for your help. That's pretty much what I've read but it's nice to hear it from someone experienced.
They said it's a 3 month process now because of covid. If they don't go in that time, we go to court, and then they clarified what you said about bailiff. I'll make sure to clarify the availability of them in this area.
When we did the tenancy agreement I did also provide them with a letter of "grounds for possession". Stating that if after at least 2 months in to the tenancy I needed to sell the property or move back in myself, they agree to leave. Both signed and dated this. Solicitor said to use it as a back up if for whatever reason the s8 doesn't go our way. Apparently it's classed as ground 1 on the s8 but takes 6 months for the courts to decide.
I never really intended to be a landlord. Tried to do a good deed and allow some friends to move into a vacant property I had. Never again. As soon as they're gone it's being sold.