Thanks flanneruk, W9London, most helpful info, much appreciated and has helped me understand the logistics... obviously the airside bus is the easiest way to go and, as you say, the risk is the same.

Ozgirl, any additional input (especially if you have negative experience ... which I sincerely hope you don't!... or useful advice) once you've done the route would be great if you are easily able to post something. Have a good trip!

Hi Suedee, hope this reaches you...
No problems with T4 to T5, we checked baggage all the way through to Paris from Adelaide and it got there!!
Transfer airside was easy, as soon as we disemabrked at T4 there were plenty of signs/people to point us in the right direction and the bus ride is 18 mins. Good shopping in T5 too, our BA flight to Paris was delayed 2 hours (they couldn't get a passenger off the plane...???) and we missed our connection to Nice but couldn't fault the T5 component of the flight.
Have a great trip..

Thanks SO much Ozgirl, really appreciate your effort to get some info posted and greatly reassured by your positive experience, etc. Sorry you had probs with your delayed flight and missed connecting flight.. it's a long enough trip without that but hope the rest goes smoothly. Enjoy the rest of your trip!

The actual bus ride between 4 and 5 takes 18 minutes. Add to that the walking and security and you are over an hour.

We landed at 5 and had a connecting flight in 4 last weekend with 3 hours in between and got home with 1 less bag which arrived 2 days later.

OH pleeeeeese don't say this.....BA has lost (found finally) my luggage twice in the last three months...We leave this week and go into 4 and out of 5 for Paris with only two hours....I am splitting up our clothes...

We went through T5 and T4 with no problems. The transfer was painless, buses waiting for us, both ways, security queues were short and the bags arrived in PHX and AMS with us. No idea if that is still the case now they are moving the long haul flights to T5. We missed that by a couple of days with our return flight

jelane: I personally simply would NOT depend on a BA luggage transfer at LHR this summer. Just wouldn't.

You can do carry-on only -- honest. A 19 or 21 inch bag for each of you will be large enough and you won't have to pray your bags come off the carousel at CDG.

Just a quick report back following my return - we had absolultely NO baggage problems going through London T4 and T5 on the way there and on the way back, luggage was transferred and all arrived where and when it should have - and that was for all four of us!

Suedee - thanks for the update. Looks like we're going through LHR next month, so glad to hear you had no problems.