Several things here!!!!
1. Avoid the LGW-TPA flight unless you are in Club World--they use the ultra-tight 777s (with 10-across in coach). You'll be much more comfy to MCO and driving 1 1/2 hrs.
2. Have you considered Air Canada GLA-YYZ-TPA--conx may not work, though.
3. Alternatively (but no BA miles) does AA still go GLA-ORD-TPA???
jl