Steve, you can open a bank account yourself, and there is no charge for obtaining a tax number. to open a bank account just go to the bank with your passport and couple of hours later you should have bank accounts in TL and GBP.
There is a mobile IsBank lorry parked behind the Didim shopping centre, usually not as busy as the main branch, just pop along and open an account.
The tax number can be obtained by going to the tax office which is the building on the left off the 1st roundabout if you go up towards Didim from the beach.
Just go to reception and tell them you want a tax number fill in a small form and they give you a tax number, not very complicated.
I only know of one English speaking solictor in Didim;
Ahmet Sipahioğlu
tel 0256 8136616
cep 0532 6111939
email
ahmetsipahioglu@hotmail.com
Another good one is Nadir Turk but he does not speak English, you would need to use a translator, who has been pretty difficult to get hold of lately.