Thanks all. I took a punt and booked the BUD b2b.
Homewards from the US to LHR to BUD in CW/CE, then a separate ticket BUD-LHR-MAN in ET (connecing to the last LHR-MAN of the day). No checked luggage. I'll report back how it goes!
I wonder if the LHR T5-T3 and T3-T5 will end up being as much of a risk to the connections as the BUD b2b itself.
Unlike my outward journey (
Understanding risks of ExEU) for this homewards journey, I can accept IRROPS forcing me into the next day if it goes wrong (although I'd prefer not too).