Firstly and you have to remeber this-Your going to be running a BUSINESS and so you will have to price accordingly.
Professionaly you will be pricing one of 2 ways, either by weight or by item. As for how much it depends but ironing can take time to do corectly and to a high standard. Look around to see what your competitors are charging but more importanly what you need to charge to make a worth while profit. Consider the fact you will have costs like materials (hangers, garment covers etc), equipment (see below), marketing, business insurance, van & insurance,fuel, tax etc-all before any profit!
Equipment wise you will need professional equipment if you want to do a proper job (especialy if your aim is commercial like B&Bs, Hotels, Restraunts etc), a good starting iron will cost around £200 while you will need a vacum/blower table starting around £300.
To build a business Ironing is slow and hard but can be done, though you will proberly be looking at Laundry & Dry cleaning as extra services as you grow. Talking of dry cleaning, you could approach you local ones to see if you could do ironing for them in return for getting dry cleaning clients for them.
Finaly i have to agree with Diane and you must do this properly and not for 'cash in hand', £5.50 ph is waste of time. As you grow how can you pay for workers on £5.50 ph, dont think you can just up the price as most of your clients at that price will drop you staright away.
J