Gaz - at this time of year, your beer is doing fine. Dont fret
Mark - Make as sure as you possibly can that said barrel is as clean as clean can be, Sounds as if it may have been used before and that is easily the most likely to be open to the worst sorts of infection.
I've had a new foam pan scrubber thing in with bleach, gave it a good scrub in and out, rinsed, half bottle of bleach, topped with hot water, sealed. Left with mix in for 30mins, emptied, rinsed three times.
Now sitting, air drying with lid off. Will sterilise before use.
BUT...
I've just picked up 120 500ml / 568ml bottles in six plastic crates, so busy bleaching / rinsing / dishwashering / rinsing those ready for the IPA :)