Poor service, excessive, extra charges and unjusified claim for damage

We are sitting in the departure lounge at Bournemoth International airport having just returned our rental car to Europcar airport office. We hired the car for 5 days and were quoted £98 online for the rental period. Upon arrival we waited more than half an hour for a staff member to arrive and had to pay a total of apporx £210 for the rental period together with a £250 excess for collision damage. A very small dent was found on the wing of the car. We feel in may of been there when we hired the car as there were marks on the car. We have no idea how or when the dent happend. Needless to say our £250 deposit is withheld thus making the cost of renting this small car for 5 days aprox £470.
Definately the worst car hire experience in my 40 years of international travel and I will advise everyone to use Europcar as a last resort. Has anyone else had a similar experience with Europecar at Bournemouth Airport?