Thanks folks, afraid I made a snap decision when you weren't looking. But it seems likely I'll be ok.
I had to go to Wickes earlier, and they had what appears to be more or less the same, but with fewer accessories for £16 (Draper branded as Wickes according to the instructions). So cheap I couldn't not get it – unlike the dremel which only has 1 collet size, it has five for example, and I have truckloads of different rotary tools with different size shanks..
My main problem has been my little Woolworths(!) tool won't take a 1/8" collet for standard dremel tools. Like John I have a Dremel 3-jaw drill chuck to get round this, but it tends to come loose.
This one is also much more powerful. than the Woolies wonder, which is 12V.
Neil