Refusal of leaseholder to pay full service charge

Other

There are 7 residential units of various sizes and 2 shops in the block. The lease states that all freeholders and lease holders should pay 1/9th of the service charge (whatever the size or position of the unit) The Leaseholder's agent overseeing the shops believes, as they are on the ground floor, his client should not pay the recent service charge increase of £50pcm (the first increase in 15 years) as decorating and refurbishing the common parts is not obviously beneficial to the shops. Up until February the service charges were paid but now each shop is £250 in arears. We have written politely to the shops' agent several times but he continues to refuse to pay the extra £50 therefore effectively breaking the terms of the lease. We would be grateful for any non confrontational pathway but ultimately it seems the only course action is to go to the small claims court. Can you advise the best way of dealing with this situation and do you have any template letters in this regard?