Just an update to say that the 14s were fine. They were bigger in some trousers than in others, but tops are fine.
I bought £200 worth of Mothercare maternity stuff for £25 off of Ebay. Most of the stuff still had labels in it that had been drawn through in blue pen. Mostly returned to store stuff, but it was all fine. One of the tops had a bead missing and another will have to be thrown because it had a small hole near the hem, but other than that the stuff is fine. It was a lucky dip really, didn't know what was going to be in the box. I got a PJ set that I was eyeing up in there (has a feeding vest, stripy trousers and a wrap over tie hoody, for sale in Mothercare for £30), 2 pairs of black trousers, a pair of beigy cords, a black stretch skirt, a couple of going out tops and 6 vests in various designs (some with support panels, some longer ones) in pink and white - all for a bargain £25.