Dave,
I would be concerned with regard to buymobilephones. When phoneboxdirect website went down it provided a link to mobileoutlet and buymobilephones sites for about a day. Strange. I suggest you have aa look at the moneysavingexpert website forums. This site has gone a bit quiet.
I would think the best option for your wife would be to take the company to court for the full amount of cash back asap. I fear that they will go belly up in much the same way as CNM/PBD after Xmas. The court process takes about a month.
Not sure if there is a thread on mse site but you could start one up and perhaps get some advice/experiences from others who have dealt with buymobilephones. There are a lot of well informed posters on the site.
Good luck, Neill