I could teach anyone how to isolate, disconnect and lift out a WC in 20 minutes. BS denotes that WC inlets should be fitted with isolators or ballfix valves. Getting over any height difference after tiling is a bit of a head scratcher to start with. But there's so many fittings available now for all sorts of scenarios. It's well worth learning how to do it. The time it takes to disconnect one and reconnect it after is far less compared with cutting tiles around, and as JB said if the pan ever needs changing....