I would contact PPL - Phonographic Performance Ltd - who look after the copyright of recorded material. Also the MCPS/PRS who will tell you about the mechanical copyright - the people who wrote what you're doing. Phone them up and ask, they're very helpful. But they are the main men so ignore at your peril.
http://www.prsformusic.com/Pages/Rights.aspx
http://www.ppluk.com/
If you're including other "producers' " work, i.e. work which already uses other people's work, then beware as you'll have many layers of clearance. This can be a long and involved process and there are people who work full time on clearance - like using samples.
This is a minefield of copyright law and will get you into HUGE trouble if you don't play by the rules!
It's much easier to write your own material from scratch and not use samples, etc, or even just to cover other people's songs without changing too drastically.
When you say label is it just for your own work or are you planning to sign other people?