I am hoping that LHR immigration/customs will not be anything like LGW last year
LGW for a connection you need 3 hours tween flights.....
Bearing in mind that you go through the usual searches etc before boarding the plane at GOA (or wherever), you arrive at LGW, walk a couple miles, past baggage reclaim, through & into arrivals (land side), upstairs, through landside check-in (without stopping), through security as if you have come off the street and then back to the same gate you just got off the plane before at
Nightmare stuff last year...fortunately I had just over 3 hours tween flights but others on my holiday did not, they had around 90 minutes and they missed their connections.
I really do hope that T5 LHR is more efficient and alot less of a hike.