Go second hand, you get a mahoosive choice of pimptastic stuff then, pretty much what you want for a grand within reason.
Or, pick up a second hand Yeti ASR-sl/Sub 5 etc frame for ~£500, and you have £500 for rest of build kit. Merlin do some good deals on new shifters/mechs etc, look out for some SH forks and wheels - should get some Hope/Mavic and good forks for ~£300. Few quid on some new cheap but light finishing kit. Job done. May spill over by a few quid, depending, but you end up with a really nice bike