It looks like its going to cost me around 180 to do an advanced riding assessment then put in for a test.
Out of interest where did that figure come from?

The IAM do a split payment scheme so you can spread the cost (there is a £5 admin charge).
With ROSPA (in Swindon) there is a lot less to pay up front (£25) and you don't have to pay for the test (£54) until you apply.

So there are ways of splitting/spreading the payments with both.