I'm a tenant, and a rather skint one at that. When I have been working, my FIRST bill was the rent. And I have always got my HB paid directly to the LL. IMO, as a tenant, the OP is NBU to kick these tenants out, the tenants are taking the bloody piss.
No-one else is offering to pay the OP's mortgage for her, are they? So why the fuck should the OP pay housing costs for a couple that have deliberately misled from the start? They signed the tenancy as both being in employment, then promptly gave up their jobs. At a time when the lady tenant MUST have already known she was pregnant. After a pie-in-the-sky abortive attempt to get a business off the ground, they now expect their LL to let them live rent-free AND extend their tenancy. WT actual F??? (Can I find a LL like that, pretty please??!!)
The council WILL tell them that if they leave before the baillifs come, then they will NOT get housed by the council as they will be deemed to have made themselves intentionally homeless - so don't expect it to be a quick fix if they DO refuse to leave, they are doing this so that they can get a council house IMO, probably because they will get a larger council house, with a more affordable rent, than they could afford privately.
But none of the TENANT'S personal circumstances is the LL's problem. And, IMO, those upthread that are saying that the OP should consider that the tenants are going to have a baby before evicting them - well that baby's parent's didn't fucking consider it before they decided to rip the OP off, knowing full well that there was a high chance that the end result would be making themselves homeless, why is this baby the OP's responsibility?
The OP is providing a house to live in in exchange for RENT MONEY. If the rent money is not forthcoming, then neither is the bloody house to live in - I should think that's pretty obvious, even my 7yo with SN could tell you that if you don't pay your rent then you get kicked out of your home, so it's hardly fucking rocket science, is it??