Just to echo BlueTui's comment, the CAA stats in recent years tend to bear out that the BRS flights to Sanford and Cancun were not full every month. The TOM transatlantic flights out of BRS were started by First Choice some years before the First Choice/TUI merger (or whatever one likes to call it) and were retained afterwards whilst the TOM flights from CWL to Florida were axed.
Although BRS tends to perform much better generally than CWL there is at least some evidence to suggest that CWL supports long haul sun flights a bit more strongly in terms of backsides on seats. Whether a lot of discounting had to be resorted to in order to achieve this I don't know but some people were surprised that BRS remained the TOM Severnside long haul airport, particularly because of the BRS runway that meant the Cancun flight had to stop at MAN outbound for fuel.
Bristol area people seem to have a default setting that LHR, just up the road, is the only place to look for scheduled long haul whilst those who want long haul charter to the sun don't seem to mind much where they fly from whether BHX, LGW or CWL when it was operational.
Perhaps the surprising thing is that Chris Browne the Thomson MD said in 2010 that BRS would be one of the first airports to see the B 787 operationally.
Thomson will use 787 to offer new destinations - www.travelweekly.co.uk
Furthermore, TOM kept the B 767s running out of BRS for another three summers after a hard landing in October 2010 led to question marks about the 09 runway and this type of aircraft in the subsequent AAIB report, so perhaps the yields were all right.
There has been speculation about the operational capability of a 787 at BRS with the proximity of a public road to the full-length parallel taxiway meaning the wings of a 787 would overhang the boundary fence. Initially this was going to be resolved with the use of turning circles but it was later rumoured that the taxiway problem had been overcome.
Last year BRS had an amendment to their planning application approved so that the slightly larger 787 (in terms of seats) than originally envisaged could be accommodated at the central walkway now being completed.