The L.E.A do provide advisers to schools to help them raise their standards which can be very valuable for schools. It helps to get an objective outsider view form someone who has varied experience. Many heads will have been in post for a long time and can get stale.
We lost our SIP (School Improvement Partner) 4 years ago in the LA cuts. Support was only provided for 'satisfactory' and below maintained schools. However, due to a few 'good' schools being down-graded to 'requires improvement' under the new Ofsted framework, we have this past academic year been given a LIP (Learning Improvement Partner). He comes in for half a day per term, so not a huge amount of time, but it is very useful (as Totstoy says) to get an outside view on how the school is performing. Whether he is an existing or ex-inspector, I don't know, but he is a consultant bought in by the LA ...
Incidentally, I also work for the LA and our social services department are also due a visit from Ofsted. I know they have certainly gone through a 'mocksted' in the last 12 months and wondered if any other sector does this before inspection? Health for example?? It seems perfectly reasonable to me - schools do mock GCSEs etc so pupils can see where they are at in their learning, so why not others?