we need info on how to get from London - around belgravia/victoria station area to cambridge by bus, train or limo. time is flexible. weekday.

and then from cambridge to heathrow - what are the options.
3pm flight home on a sat.

Trains from Liverpool St. Station or King's Cross take under an hour to Cambridge. From Victoria, the Underground to King's Cross would be the fastest. If you have lots of luggage, take a cab.

From Cambridge to Heathrow, you can take the train back to King's Cross and get on the Underground at King's Cross--the Picadilly Line goes straight to Heathrow--allow 2+ hours from Cambridge.

Again, lots of luggage might be an issue in negotiating the transfer from train to Underground.

I would check on a car service from Cambridge which would bypass London and would take around 90 minutes, maybe less on a Saturday. The service should know how much time to allow. If there are two or more people, this may also be cost effective.

You can look at your options on www.nationalrail.co.uk where you can plug in departure times and look at alternate routes.

The easiest way from Cambridge to Heathrow is the direct bus,

Average 150 mins, every 45 mins or so, round the clock. www.nationalexpress.co.uk

You won't find a taxi doing it for under £100, and taxis will still take around two hours.

A taxi shouldn't take more than 90 minutes, particularly on Saturday.

I would not recommend National Express buses to anyone.

I've taken the bus from Cambridge to Heathrow and it was fine. It was a bus, so my expectations weren't high, but it was fine.

<<< I would not recommend National Express buses to anyone. >>>

Why?

From my experiences, the buses were filthy and the drivers surly.

Yes, they are generally cheaper than other modes of transport, but it's not worth it to me.

Anyone else agree that merely shows how little experience the previous poster must have of National Express?

I'm not at all reluctant to admit I only took National Express four times--four nasty experiences were enough for me.

I've taken National Express from Heathrow to Leicester several times. Found the trips to be fine and would do again.

I've also used a car hire to do airport transfers and think this might be a good way to go -- especially with luggage and a tight schedule.

The most recent bus trip I took on National Express was less than a year ago. It was between Woking and Heathrow. It was totally fine.

If you take the National Express coach from Cambridge to Heathrow (that's what I would do personally), make sure you know ahead of time which heathrow terminal you need. The coach makes 3 stops: T1/2/3; T4; and T5. The coach driver would need to know which stop you need before you board the bus.

I've probably been on 30 or more Nat'l Express coaches over the years. Don't recognize anything similar to what Cijt describes. 100,000% better than any Greyhound bus I've been ever been on.

A taxi from Cambridge to LHR is ludicrous IMHO. National Express is easy peasy - Cambridge > LHR w/o fiddling into London, and w/o the expense of a cab . . . .

Regarding the expense, I know there are deals on National Express, but as OP said "we," let's assume there are two adults, not seniors.

Two fares on NE from Cambridge to Heathrow on a Saturday show up over 50 quid apiece, economy. Purchased way in advance, there may be better deals.

If you count NE trips to include the rail links from Reading to Heathrow or Heathrow to Woking, I've taken about 8 of those and they were all right.

The trips I've been on of 90 minutes and more have been awful--blocked toilets, rubbish in the aisles. I have no reason to make this up. We can agree on Greyhound, however.

I've taken the National Express bus from Cambridge to all four London airports. It's a cheap, reliable way to travel, tickets are bookable online and you don't have to drag your luggage all over the place. Best way to go as far as I'm concerned.