Any idea why the hotel rooms are so pricey
It will just be simple supply and demand. Bristol doesn't have that many hotels when it comes down to it, so there are just nights, sometimes, where there is nothing decent available short of £150-£200.
I've stayed in The Bristol, often, for £99 incl. breakfast and parking (the latter normally being £20+) and The Radisson Blu for a similar amount. I've even stayed in the Hotel du Vin for around £120 per night. Tomorrow night looks like one of those nights where even the Premier Inns look expensive!