LittleSpade the Mothercare ones in their maximum size don't even fit my pre-pregnancy boobs. 
I was a 36HH- these are a little tight now, and am spilling over... SiL is nursing bra trained, works in a department store and says the main thing is that the underwires are still back near my armpits and not any further forward (then gave me a lecture about properly fitting bras) This is still the case with my bras, but they don't fit at the front any more.
Bravissimo do bras for the over-boobed ladies of Britain and elsewhere- but their nursing bras go up to a J or K maximum and I'm pushing that now, never mind in 6 months! (got to be a JJ already, at LEAST).
I'm despairing really!
Think I'll have to stick with my usual favourites in a couple of sizes up, if available, and then who knows where I go from there!
Must find a gigantic boobs thread...
Winky they thought I was 13 weeks too, which is utter tosh, unless I ovulated twice and one of those was 2 days after AF finished (balls). As someone else said, further up the thread, the peanuts might just be having a growth spurt right now, and they'll level out later. The figures they work to are averages, after all. And we're not average, are we? I'm certainly not!
I'm still thrilled that although the baby wasn't moving much, even the sonographer getting me to shift over and over again didn't get them to move. Ha. Peanut is stubborn like me! Dad is delighted- he thinks 'he' has inherited some of his grandad's personality 