ok, so on my chromatic tuner there are various keys i can select...Eb,c Bb, F..etc... which is the correct one i should be using?
also an explanation would be massivley appreciated thanks in advance.
you're not after a key, just a tuning, standard tuning is E A D G B E. What do you mean by that?

A chromatic tuner means you can pluck a note and it will tell you what pitch it is at, non chromatic tuners usually are set up for standard tuning and sometimes have preset tunings, usually using a dial of some sort it will only tell you when you get the note to that preset tuning. The chromatic tuner tells you what pitch you are at in real time all the time, which makes it much easier to tune to Eb or other not so common tunings.

Does that help you any?
not really :S.... i mean, i understand standard tuing...however the key obviously does something as ive just tuned to Eb key and it sounds lower...is there a correct key to be tuned to is probably what im asking..e.g concert pitch....
Does it actually say the word "key" on it?

If not, just put it on "E" as that is what standard tuning is sometimes referred to as.

If it does say key, I have no idea as I am a noob in music theory. You might have some luck in the music theory forum.

Sorry bro!
Do NOT look behind you.
what tuner do you have?

Eb is lower than E by 1 semi-tone or half step.

You may not have a chromatic tuner, its supposed to simply tell you the pitch of the note you are tuning, there shouldnt be anything else involved but with the wide range of tuners available its hard to say for sure.
Use the tuning only thread stickied at the top of this forum.
Been away, am back