ssd - Thank you. Please excuse ignorance i don't know what the set up is in Scotland.
Basically the quality assurance can be done for yourself individually ( or i believe through the NCMA) or through the network in your area (in my case Oxon/wilts is Trio)
It is supposed to be a guarantee to parents that you are offering a high quality service etc. You also need to be quality assured before you can go for accreditation (offer free places to 3-5 year olds and government pays you)
The network will also visit you after you have gained this to ensure standards are kept high and will carry out inspections like Ofsted. May according to rumour lead to shorter ofsted inspections.