I was in Charles Fox in Covent Garden yesterday, and they've recently started stocking Illamasqua there.
Many of the Illamasqua products are manufactured by Kryolan, and very similar products can be found within the Kryolan range - particularly in the powder products (blush and eyeshadows.) Illamasqua's liquid metals are also extremely similar in texture to the Kryolan metallic supracolors, which come in gold, bronze, silver and silver-green colours. I have absolutely no problem with this - Illamasqua is more expensive than Kryolan, but the packaging is a lot nicer and Kryolan, like most other theatre ranges, isn't easily available to many people. Also, with Illamasqua you get the help of the makeup artists at the counters when choosing colours, and advice on application techniques.
I don't understand buying it at Charles Fox though - why would you buy Illamasqua there when the Kryolan is a couple of feet away in the same shop? You're not going to get any more help choosing Illamasqua in Charles Fox - the assistants will sell you stuff, but the shop is for professional makeup artists and performing folk, and they won't fall over themselves to help with colour choices from any of the ranges they stock. Why would you buy an eyeshadow for £14 when you could get pretty much the same thing right there for £5?