As churchy says, and I have to agree, MIA is a much better route. You'll also find ex-EU fares to MCO via MIA cheaper than the direct flight from LGW.
And:
CW on a 747 to MIA is great on the upper deck
Lounges are better at LHR and Miami.
Less kids (even if you've got them) I have found on the MIA route, so less chance of being kept awake
No chance whatsoever of a POUG or AuP or OpUp to F as the LGW-MCO is 3 class

I stopped using LGW to Florida years ago