Hi and welcome to ExTS
We don't recomment specific hardware or machines as, if you are unhappy with your buy, you will automatically blame us :)
What I can do is point you in the right direction.
1. Make sure that the version of Windows is 64bit and Win 10
2. A Solid State Drive [ SSD ] is a lot faster than a standard Hard Drive.
3. 4GB or more RAM
4. Intel Xeon/Core 2 Duo or Quad /Core i7 or AMD Opteron/Phenom processor
5. Stay away from onboard Video Card.
Having said all of this you will be hard-pressed to find these specs on a machine for £400
You could compromise on the Hard Drive.
To manipulate graphics you need the best specs that you can afford.
DAZ Studio does not require a machine with particularly high specs [ look this up ] I did, however, read a few reviews that certainly didn't recommend it :(
You may find this useful reading - click here