I ended up getting imitiation firearms from Warwicks. There was no need for an armourer as the guns were all plastic moulds and incabable of hurting anyone. All the gunfires being composited in post.
I notified the police and council so we weren't mistaken for a group of heavily armed bandits.
I definitely recommend the imitation guns for any low/no budget shoots, muzzle flashes can be easily composited and look great if done right.