arriving 10am heathrow. our next flight is 4pm out of gatwick. i see nationalexpress? busses leaving every 10 or 15 minutes. do we need to make advance reservations? if so, do we need to pick an exact time for a bus? i thought that because there are so many busses, we could just show-up, pay, and board. what to do?

All the Londoners are asleep at this point, so I thought I would reply.
Based on their policies, I would wing it and expect vacancies.
Not much chance of changing a reservation while in the air.

Our conditions of carriage state that if you miss the coach you are booked on, through no fault of National Express or Eurolines, and you do not cancel your seat before the time of departure (longer on Eurolines services) then the ticket is no longer valid and is not eligible for a refund or amendment.

However, at airports we do try to help as much as we can. Under normal circumstances we will try to accommodate you on a later departure, subject to seats being available. But we are under no obligation to do this.

All the folks in the UK aren't asleep NOW so topping this for you...

I'm having a sleepless night in the US.

Icethecat quoted two paragraphs from the National Express site. The next paragraph reads, "Our advice when booking is always to book on a service slightly later. Then, if your plane arrives on time or early, and you are in time to catch an earlier coach, we will be happy for you to travel on an earlier departure - subject, always, to seats being available."

With 6 hours between flights, you should be fine without reservations for the bus.

I looked at this because I was curious to see why someone would want to be kissed from Heathrow to Gatwick, but I figured out that it was BUSES of the transport type that were involved.

I agree with KidstoLondon that you've got enough chances at buses that even if the first is sold-out (which is doubtful) you won't have a problem getting on the next one. I'd wait and purchase the ticket there.

We have to do the same thing.London has some great shops.Don't have time to drop into one shop like "Top Shop"?
Would it be extraordinarily expensive to get a taxi swing by a shop and then off to Gatwick?I don't know the layout to London.Hopefully someone can answer.Thanks

I don't think it's very practical to go into London in between the airports, both because of the time & cost.

London's airports are really shopping malls with a few runways attached: there were branches of Arcadia (Top Shop holding company) shops at Gatwick last time I specifically looked, but check on the Gatwick website.

And anyway, Top Shop will be opening in the US later this year. You won't see any change from £150 for a prebooked car from LHR into central London and on to Gatwick (and a cab off the rank will be a lot more). It'll take at least 3.5 hours in driving time alone - and an AWFUL lot longer if you get the timing wrong

Shop at Gatwick, or wait till Top Shop hits New York.

Almcd, both "buses" and "busses" are acceptable plural forms.

Thanks Cotswold

thank you all! think we'll get tix when we land. i assume the place to buy tix is near and obvious. verification, please.

We have to do the same thing, only we arrive at heathrow at 8am and our flight from gatwick doesn't leave until 7pm. We figure we've got plenty of time to go into the city and have lunch, but where should we go? Any suggestions for great restaurant and maybe a sight to take in that wouldn't have us too worn out?