well young lady! i would have to say that it is normal to replace the waterpump at the same time as doing the cambelt as a new cambelt will put even more pressure on a worn waterpump and could cause a failure of the waterpump bearings. please note that only good mechanics do this...the backstreet butchers will normally just throw on a cambelt and take the chance.
i would suggest that the belt that was heard slipping was your fan belt/alternator belt , as a cambelt is a toothed belt which cannot slip unless extremely loose and then it will jump round a tooth or two and you have a wrecked engine...instantly! ahyhoo, if all of the above are being replaced and genuine vauxhall parts are being used also considering that mechanics time is usually charged at around �50 +vat per hour (this job should take no more than two to three hours) i would say that you are being overcharged. if it's a vauxhall dealership that is doing the work then the price you quote would be about right as they seem to charge a higher hourly rate for mechanics! hope this has been of some help. as an example,i have just done the same to a 98 ford mondeo and charged the guy �230 including genuine ford parts and labour.