Yes I've done it. The staff will be VERY rude to you indeed and quote security reasons (which I have on both occassions - Gatwick and Luton spoken to customs about and been told that it is bollocks).
The will insist you get off the plane and wait at the gate (then you become ground staff problem and they can go home or turn the plane around), but still do not get off the plane.
The will insist that 18 people require disabled assistance and you will have to wait over an hour to have your turn (bollocks again - they turn planes round in half that time).
You have to be quite brazen and confident and determined.
They will ask you how you normally manage. They will ask you why you can't carry them. They MAY even threaten you with the police (to which you reply 'Thank goodness, yes, do get someone reasonable here. Although why you would want to waste their time when you could simply pass us our buggy I don't know').
They MAY offer someone to carry your bags but this will be a ploy again to get you off the plane.
Eventually they will either get someone to retrieve your buggy from the carousel, or they will bring you a disabled buggy (After other disabled have been taken).
If you, and I and every other mother made the same fuss they would surely change their policies.
Ryan Air, much as I hate them, usually always give you your buggies btw (which just goes to prove it isn't a security thing).