Assuming your BOS-LHR is ontime or early, I would clear immigration using the e-gates, then, depending on the time, head for the arrivals lounge or straight to the First check-in area to use the dedicated security queue, which will dump you directly into the F lounge. There often is a wait for a shower in the F lounge in the morning, so if you really want a shower and have the time, I would make a quick stop at the arrivals lounge (keeping a close eye on the time, as you note). If you are able to stop in the arrivals lounge for your shower, then head to the F check-in area to clear security.

If you land at T5B or T5C (which I suspect is likely, unless you get a bus gate), I would suggest checking the monitors to see if your MAD flight leaves from T5B or T5C. If so, you’ll be able to use the much faster transit security at T5B and get a shower in the T5B Galleries Club.

However, as it’s very possible one of your flights ends up in T5A, it’s also good to know the T5A options. (Indeed, I don’t know the likelihood an IB flight will end up in T5B or T5C, as I haven’t paid attention to the gates the IB flights tend to use.)

Thanks for the replies. Assuming the flights do require me to go to the A Gates and the incoming is more or less on time I'll go landside following the recommendations in the guide thread, and then see what the time is.
Is there ever a wait at the First security?

Hi.

Normally the first security is pretty quiet or 1 or 2 people un front but early Monday Moring can be peak time with longer queues. When will you be at Heathrow?

Regards
Tbs

Jumping on the back of this thread. Next month we are coming back from SIN on BA0012 in CW, followed by a connection to MAN on the 8am shuttle but not in Club. Will we have access to the Galleries lounge due to coming in on a CW ticket or would we be better going landside to the arrivals lounge for a shower before the final leg?

Hi.

Yes you will have galleries club access based on cw sin lhr I would keep your boarding passes.
What time do you arrive as arrivals have more showers and the galleries club showers can gave a queue later in the morning

Regards

Tbs

Landing 9:00am and departing 10:40am on a Monday, so hopefully that's after the peak.

Hi.

That will be after the peak but you will need to be at the scanner at the entrance to security at t-35 ie 1005 at the latest for conformance
.regards
Tbs

Scheduled to land at 5:15 so hopefully be some of the first in the Club Lounge?

hi.

should be ok then. I think the 2 flights from hkg get in just before you

regards

tbs