We travelled with United Travel (Ph: 2832555/2884346). Short-stay prices range from £299 for two nights at a 3-star hotel to £549 for two nights at a 5-star deluxe hotel. (Prices include return transport between Prague airport and your hotel.)
Hotels will provide you with tickets for trams and the metro. Tour buses, jarveys and walking tours are also available and are ridiculously cheap. You can even have a cruise on the Vltava for £2. It can be quite cool when the sun goes behind the clouds and showers are occasional, so carry some light waterproof outer wear. And bring a good pair of walking shoes.
One word of warning. Exercise extreme caution when using the taxis. Quite a number of these capitalist entrepreneurs share the enthusiasm of their colleagues everywhere for fleecing the unwary tourist. Always ask first how much the fare will be before you get in and always make sure the meter is on.