Thanks for the replies guys.
Steve, the tuning is fine without the capo. When I put it on, I have to loosen the strings a fair bit as theyre quite sharp. When I take it off, I have to then sharpen the strings again. The guitar holds it's tunings fine, it's just that a capo seems to take it way out!
Thanks for that advice John, I'll try to leave the capo a bit looser. Problem is, I'll get buzz from the bass strings if I'm not careful.