Blinc conduct insurance-standard/regulation compliant tenant checks/references. It costs about £50 per tenant and you get a report which you can keep on file. You also need to make sure you take proof of current address and keep that. Then you can get landlord insurance which includes legal costs and representation should it come to that. Depending on how important the income is to you, you can also protect your rental income via insurance. Blinc insurance is expensive, but you can use their tenancy search report to obtain insurance with another company.
You need an annual gas safety check. You have to have electrical regulation compliance certificates every 5 years. EPC every 10 years. You have to give the tenants copies of all these certificates. You have to give them Rights to Rent information.
You have to register their deposit with a protection scheme and give them copies of the paperwork.
You have to have carbon monoxide monitors and smoke alarms in the right numbers and places for the property. You have to have locks that comply with the regulations and facilitate an uninterrupted exit from the building e.g. thumb locks on external doors, not a lock that requires a key. All furniture provided has to be compliant with fire regs.
I get an inventory done by a third party inventory clerk, which tenants sign. It includes photographs and detailed descriptions of the condition of everything. Since the inventory will be the key to resolving many of the disputes about the deposit that could conceivably arise, I think this is money worth spending; but I know other landlords do it themselves.
So yes, you do need an assured shorthold tenancy, (and you would not believe how many people sign these without reading them) but there is a lot else to do.