I would think around 20 euro an hour would be reasonable. A typical house survey and the design of an extension to planning and associated drawings should take approx 40-60 hours to do (depending on size & complexity in many instances this can be significantly longer), then there are associated extras, printing, planning fees, newspaper ad, postage, lamination of site notice etc.
Hopefully this gives some idea of costs - however the above charge per hour would be based on "nixer" rates, if this guy is set up properly as a sole trader than the hourly rate would be more in the region of 40 / 50 euro per hour to cover tax, accountants etc.
Bear in mind that the fastest office might churn out a planning application in one week of a basic extension to a simple medium sized modern semi-d, some of the countries more renouned architects may spend several weeks or months developing a design with their clients. With the figures given above you should determine if this guys bill is reasonable and if not discuss the areas of discrepancy with them.
Hope this helps.