Wow $800 for a car failure on the bridge
sheesh I hope you didn't lose an engine over that, I'd probably have let them tow me and pay the bill rather than risk losing the head on my '87 diesels. Definitely better than a $2500+ repair bill
in the states a new water pump sells for about $170 or less depending on where you buy it. Its considered a DIY job if you have the tool, the serpentine belt on its tensioner pulley is a bit tricky but this is not a tough job, easier than on some cars where the entire radiator has to come out.
They must be charging full book price and some padding to try to get $700 for that job.