UCL is probably a reach, as you are only taking Calc AB, and they ask domestic applicants for grade A in Maths A level for the combined course, which is usually regarded as equivalent to (actually a bit more advanced than) a 5 in BC. If you do get an offer it will likely be conditional on getting 5s on all this year’s APs. The straight Econ course is likely to be out of reach, they want A* at A level, and I don’t think your mathematical preparation would be strong enough.
KCL - probably also a reach without BC but easier than UCL I think.
But congratulations on getting into Manchester, especially unconditionally!