I did this less than a month ago and made it with 10 minutes to spare (but I started with 90 min connecting time). Inbound was late (AA DFW-LGW) and outbound was spot on time (LGW-MAN). Long walk to make international to UK domestic transfer -- much shorter if you are doing international transfer. Huge line at immigration (I am not UK but luckily had fast track, however fast track was closed and I had to beg to get them to open it, would have missed the outbound flight otherwise). I would say you have to have an on-time arrival, be quick off the plane and walk briskly to make it. It is much worse than LHR T4 connections, for example (at least for non-UK citizens). Presumably BA arrives at a better gate, which will save you 5 minutes, but it is still surprisingly difficult to transfer at LGW.