Due to a change in circumstances I am considering renting out my flat,
which is in a purpose built block in a good rental area.
I have to pay a quarterly service charge, council tax, etc and it would
be rented furnished (unless there's a good reason to rent it
unfurnished).

Regarding things like service charge & council tax. Is the tennant
responsible for paying them or should I build them in to the rental
price and pay them myself? I'm concerned about what would happen if
the tennants didn't pay.

Obviously I would like reliable, hassle-free tennants and for
everything to work well in the flat so I would have as little
involvement as possible. I wouldn't have much time to work on repairs,
chase late rent, etc.

Would you recommend getting a lawyer to write an official rental
contract or just do it on a handshake & deposit and should I hand it
over to an agency or do it myself?

Thank you.