I flew into T5 from Spain last friday.

I wasnt actively looking, but I seem to recall a cordoned off area to send those from Red zones at immigration (from memory it sent them right to the end of the immgration hall). There were also staff asking specifically if anyone had flown in from India. After immigration (egates) there are red zone signs and then another seperate area for red zone arrivals at baggage reclaim.

I arrived around 1.30pm and it wasnt very busy. Egates are back open with Border force checking PLFs etc before admitting entry to the egates. I strongly urge you to print off all your documents and clearly identify which one is which (I used post it notes). The staff were very grateful that I had done that and it is those people who show everything on their phones which is what takes the time.

I understand your concerns and everyones perception of risk is different. I think it is worth remembering that almost everyone going through arrivals will have had a negative PCR test which, whilst doesnt elminite the risk, it reduces it significantly.