Yes it is a business regardless of where it is. You still need to display the correct methods and carry out the same procedures required by COSHH, Fire exit signs so your client knows how to leave the house, data protection methods if applicable, insurances, first aid kit, eye pods, fire extinguisher, consultation forms, accident book in case your client has an accident, falls over in your room, throws coffee on themselves and receives a burn etc. You have no need to contact environmental health and I don't believe you require a H&S poster as you are not involved with staff and this is predominantly for staff so they know who to contact regarding H&S issues..... it would be interesting to see how many people actually do half of this! However there are threads on here that state mortgages may cause an issue and you would have to switch from a residential to a commercial and then pay commercial rates. However I am on the understanding that the problems generally arise firstly if you mention it and secondly what business is it that you are carrying out. Building Insurance needs to be updated to.