Hi Matt,
It sounds a lot but I am not sure what current labour rates are.
The Clio is a very easy car to fit an alarm to as all the connections are easily accessed so they should be able to do the job easily and quickly.
I put a concept 650 in my Sons 172 in 4 hours, that included stripping the crap Cobra one out. All done to VSIB standard. (I was Clifford trained)
The remote start needs to be done carefully with a safety switch on the gear change no matter what your told. Accidents happen.
Both alarms have prox sensors and I would always fit a glass break detector or level sense monitor as a back up.
I dont know which dealer you are using but there are quite a few in Surrey so it might be worth shopping around,
I would recommend Wentworth car Audio.
http://www.wentworthcr.co.uk/carsecurity1.htm
They advertise a Concept 650 fitted for £399 so worth a check.
or phone Clifford and ask for a rec. They know who the good dealers are.