Heathrow / flight connections?

Can we still use the flight connections centre/buses if we have to claim our bags from a BA domestic flight and check in for an Eygpt air flight to Luxor? (and the reverse on our return from Cairo)
The BA site and the heathrow site have confused me (doesn't take much) they say that if you have seperate tickets - which I assume we will have, you have to check in bags for the Luxor flight, as they won't be through checked - if you go and collect bags at T5, can you still go through flight connections and go to T3 or do you have to go through the whole arrivals process and then proceed as a 'new passenger' as it were? If so, which is the best way of getting to T3 from T5?
It's all beginning to sound like a huge PITA.
It's the last time I let a TA book my flights - if I'd have known that BMI fly to Eygpt I would have booked direct with them - the bags would have been through checked then.[n]

[honey lamb]

You won't be able to use Flight Connections if you have to reclaim bags and check-in for your onward flight. There are no facilities for checking luggage at the check-in desks in the transfer area. This means it is as you say - you are effectively a 'new' passenger. The best way between T3 and T5 is on the Heathrow Express which is free for transfers between terminals. Just follow the signs and be sure you get on the right train otherwise you could find yourself in Paddington [:0]

Hi Staffskite - Is the Egyptair a codeshare with BA or have you been booked in under the Egyptair flight number?

Thanks honeylamb, I thought as much - so you have to go through security etc. again at T3?
It's a few years since we had the 'pleasure' of LHR but that was with VA TO Miami with a domestic BMI flight so we were through checked and used the FC bus. I couldn't remember where we ended up after getting to the terminal, but I'm guessing it was in departures, after security?
Three hours between flights is beginning to sound insufficient. We have a 11 am flight from MAN and a 3pm flight to Luxor.
Baloobear - BA don't code share with Egypt air (BMI do).
I will now start having nightmares about being delayed out of MAN.

[honey lamb]

A few years ago, indeed until very recently, you could through-check your luggage between most airlines regardless of whether they were partners or not. However all that has changed and by and large it is only if your flights are on the same ticket (but I always feel it does no harm to ask)

Yes you will have to go through security again in T3 but three hours should be OK. Most airlines say two, but I personally would be happier with three