Unless someone is employed under a scheme laid down by law (such as teachers) or there is a formal agreement between the employer and a trade union (agreeing to common conditions for all employees), every employee's contract with their employer is entirley separate from any other employee's contract.
As long as an employer doesn't breach legislation on discrimination (relating to sex, race, age or any other factor covered by legislation) or fail to meet statutory minimum requirements (relating to pay, holidays, etc), he's free to enter into different contracts with every one of his employees. For example, two people might be doing the same job. One could be paid �5.35 per hour (with 20 days paid holiday) and the other could be paid �1000 per hour (with 100 days paid holiday). As long as there's no discrimination on the grounds of race, sex, etc, it's perfectly legal.
It may well be possible that staff in your office were originally employed by a different company which has since been taken over. Although the new employer would be obliged to ensure that employees of the firm which was taken over were no worse off than under their former employer, there would be no obligation on the new employer to bring those new employees' conditions into line with those of the rest of the firm's staff.
Chris
PS: if you were thinking that giving fewer holidays to staff in Scotland might be racial discrimination, this would only be the case if English staff in Scotland received the higher allowance and/or Scottish staff in England received the lower allowance.
PPS: I wish people wouldn't put the words 'Scottish' and 'Newcastle' in the same sentence. It makes me thirsty ;-)