Getting around LHR

[in limbo]

Hey there guys and gals.
I was wondering if anyone with experience getting around LHR could lend a hand.
I will be arriving at terminal 4 and need to get to terminal 3. I have 3 1/2 hours to get this accomplished.
Is there a terminal train or bus? Do I have to go through immigration then head over to terminal 3 ?
Any help would be appreciated.
thanks
IL:ok:

[Rollingthunder]

Go through immigration and then follow signs to the Heathrow Express (train). Free between the terminals. Every 15 minutes.

[Globaliser]

Are you connecting to another flight from Terminal 3, and can you get your bags through-checked? If so, you might as well follow the Flight Connections route and stay airside. The process is:- Follow signs for Flight Connections Terminal 3 Be taken by airside bus to T3 Clear security Go to transfer desk (if necessary) to get new boarding pass Go to gateIf you can't get you bags through-checked, then you will have to clear immigration, collect your bags, and clear customs. Then, as Rollingthunder says, take the Heathrow Express to the next station which serves Terminals 1, 2 and 3 and then follow the signs for T3.

[in limbo]

Thanks for the responses.
I am arriving from JFK on BA and taking a GF flight to BAH.;)

[Globaliser]

Next question: Is this on one ticket, or two separate tickets?

If it's one ticket, BA will through-check your bags. If it's on two separate tickets, BA policy is that they won't through-check, so if they stick to that you'll have to do the reclaim at LHR T4 and schlep over to T3 landside. (Always worth asking, though.)