Hi Mark,
welcome to the forum. It would be helpful to yourself if you could spare the time to introduce yourself to the other members, you can do this on the link below:
http://www.dj-forum.co.uk/index.php?showforum=13View some of the other intros to see what others do - we all have to start out somewhere, but it would be good to know more info about you, where (roughly) you're based, and what type of gigs you would want to cover.
For example, if you were in my area - then I may have some older gear I could offload. Getting to know other DJs in your area will help.
For £400, at 1 weeks notice, you'll be pushed to have the time to get gear in, tested and familar with it.
Ebay would be a sensible 1st choice, but most stuff will require collection - and you really need to see the gear working.
Without knowing what else you have (CD Players? Mixer?), its hard to know what to recommend.
With such short notice, you should be able find a hire shop to fill in any gaps of gear you don't have.
If you don't have any gear, then you can try to find average quality gear on ebay/here, and hire in what is needed, acquiring more gear as you get more gigs.
I assume you're charging for this gig?
From my local hire store;
DIY Disco 2:
-Basic Dual CD Player+Mixer
-Amp
-2 x 12" 200W Speakers
-Mic
-1 Lighting Effect
-1 Mic
-Cables..
£60 Per Day...
Assuming you're charging more than £60, this will get you out of trouble and you won't make a loss.
Check the for sale area here;
http://www.dj-forum.co.uk/index.php?showforum=49Active speakers generally cost more, a budget 12" Active (LD Systems Bi-Amp 230W) are £178 each new.
On ebay, some SkyTec 300W (max) at £124 each new.
A small battle mixer ~£50, Mic £10+, CD Players...?, Headphones £10+.
If you do manage to get some gear - also try to get a bit of black cloth from the local market to drape over the table to hide the wires and make it look a bit tidier, this will only cost £5max for a few meters.
You can get away with a small set-up, but if you keep it looking tidy.
What you play, and how you play it will probably win you more gigs than top-notch gear for a pub gig, so set-up early - introduce yourself as the DJ to a few people (before you start), and hopefully it will be a good night.
Good luck,
Jason