I will tell you now, most council contracts come with an obligation of reconsigning a union. I took one on 3 years ago and it has proven to be profitable. but to let you know what you may be in for, TUPE, TUPE, TUPE. I can guarantee that the union is involved in there if it is council I had 6 employees and 5 were a member of the Union, it was two unions but officially you only have to recognise one I think. But be prepared to talk with a bullpoopter that knows what they are talking about. If your ducks are not in order they will eat you up. The cost of joining the LGPS (local government pension scheme) is not cheap. I had to pay for actuator fees of 1400 GBP and then I had to pay a bond (I am a small company) of 8000 GBP which I had put up by a company and it cost me 1200. The original bond they asked for was 80,000 GBP and you have to put up a specific argument to get it lowered which, if your situation is the same I will talk to you about.
But I can not stress more than enough, the law says you can not take over a contract without offering the current employees the job with a few exceptions. 1. If the job is carried out by the owner of the company currently servicing the contrat (a small company as you are planning to do). 2. The current employee has been there less than a year (you will still need to do TUPE due diligence and take them on but pretty easy to get rid of later if necessary). 3. The current employee work at the site is less than 50% of the employees total work (some HR companies will say 70%) by that company (they work other sites). If there are empolyees there, there will always be some type of TUPE implication and you better be aware, and you better be aware of the cost of LGPS.
Now saying all that I have 95 hours per week, and the council was charging 8.92 per hour, but the place paid for cleaning equipement and chemicals. I charge 9.20 per hour and had to fix problems. I talking big problems that had big Union implications (I had fun with that one because I am meticulous). Even though I charge them more, they were being charged for 105 hours for around 70 hours of work, and this had been going on for years so the union had problems with me changing that, but they finally seen it my way and make a good profit on it now.
Be careful, know what you are getting into and go for it.