A while ago I submitted a building control notice to convert my
attached garage into living space (Utility room and study). Shortly
afterwards I received a letter from the planning office saying that I
needed to apply for planning permission (with plans + full fee of
£220!).

At around the same time the documents came through from the solictor
(we had just bought this house) and the original planning permission
granted for the 2-storey extension that contains the garage (ground
floor Kitchen + Garage, 1st Floor Bedroom) had a condition attached to
it that the garage must remain a garage to preserve on-site parking.

What led me to believe I could convert the garage in the first place
was the presence in the locality (on my street and adjacent roads) of
other properties where similar works had been carried out.

Does anyone have any experience of dealing with planning departments /
getting conditions removed or establishing planning precedents?

Another thing I cannot understand is the that they require the full
fee for the planning permission. For £110 you could make an addition
(extension, conservatory etc) but for change of use the full rate is
levied.....why?

Thanks