Hardware switch/router/firewall appliance to assign and restrict fixed ip to ethernet port

Hi experts!!

First post on here for a long time so forgive me if this is already answered somewhere.

I am setting up a mini server room and offering my clients a co-location service for small servers mainly used for offsite backup, ftp, calender and non mission critical web hosting.

I have had a leased line installed and currently have 64 fixed public ip addresses given to me by my provider.

I want to offer the ip's out assigned to my customers (up to 2 ip's per customer) so they can co-locate a small server in our server room. I will be giving them full control of their co-lo server we install for them. Each customer will be given a small server and 1 or 2 ports on the switch/appliance.

I need a cost effective hardware appliance that will allow me to assign a block of 1 or 2 ip's to each customer but also need to make sure the that the appliance limits them to the ip's i give them, for instance if they accidentally add the wrong ip to their server which would then conflict with someone elses in my range of 64.

I also need the ability to monitor and/or restrict the bandwidth usage per customer/port

Lastly i would really prefer something that has a web gui to make it easy for me configure as I have little CLI knowledge.

My budget is up to £500 but i would like to spend less and consider second hand equipment, I was wondering if there was a 16 or 24 port switch/router/firewall appliance that would do this task but if there is a better way of doing this i am open to advise.

Thanks in advance