Need Van/Station Wagon type Taxi at Heathrow

Hi guys..i am looking for a van/station wagon type taxi to pick us up at Heathrow airport . Does anyone know any reasonably priced taxi companies that do have super sized taxi's ?
I know there are private folks that taxi people around..but not sure if they will have the large cab we will defintley need...besides i think they have banished those guys from Heathrow anyway.

Any tips is much appreciated..i know they have lockers at the airport if worst comes to worst and we cant move our suitcases ( 5 large ones ) but hopefully i wont need to ( 15 pounds sterling a day i think it is)

Thanks
Zufan

just an FYI-we use non black cabs from heathrow sometimes-you just call the cab company when you are ready to be picked up and they get you.  they just can't wait like a normal one.

I always use a local mini-cab service back and forth to Heathrow for work.   The company I use is pretty big and very reliable.  Meadway - http://www.meadway.com/

The definitely have minivans, I think they call them people carriers though.  They'll meet you just outside the customs exit at the airport with a little sign and help you with bags. 

Call a local mini cab firm they all have estate cars or people carriers.