time needed to transfer from heathrow and get to gatwick

I did the reverse last weekend and after much research on the Internet decided to go for a prebooked car,which worked well. I don't have the link to hand but the company is something like London airport pickups and they were somewhat cheaper than others. Very professional. Regardless of how you decide to do it, the time you have is relatively short and to me worryingly so if you decide not to do the booked car. My flight was early but I spent 35 to 40 mins in the passport control queue...admittedly this was Gatwick but the same could happen in LHR. The drive between the 2 is meant to be about 45 mins but in reality took closer to an hour and that was late Sat afternoon. if you are doing this on a weekday, I am guessing traffic could be an issue but others will know more.

Thanks I just found out that there is BA flight from LHR, Term #5 that leave at 11:10 AM to MAN. It's a 2 hour layover (if I was leaving from GAT, I would have a layover in MAN) and I will connect to my orig. Flybe 3:25 PM flight to INV. Hopefully all this work out. They might change flights before I do my finally booking. Again thanks

I personally have never had to do this, but I think you would be pushing it if you try. As you know you should allow at least an hour (could be longer) to go thru immigration, 10-15 minutes to get to where you need to catch the bus, 1 hr 30 minutes bus ride to Gatwick (could be longer if the traffric is bad), then an hour (or longer) to go thru security at Gatwick. Here is a website you might want to look at.....http://www.moneysavinglondon.com/Heathrow-and-Gatwick-airport-transfers.html

Thanks for all your comments

i would play it safe and do the flight to Manchester from heathrow. Why put yourself through the agony of an anxious ride to gatwick, and probably still not make it.