Not sure exactly what switches they are but they are not high end ones. I think they are procurve something
In terms of bandwidth, we mostly need for internet access to submit data as forms or attachments and accessing the server.
Server is used as a data store for IRIS and Sage so all of the users will need access to them.
We have bog standard netgear prosafe ones and they support port trunking - although we've not had a chance to actually try it yet as one of the switches decided to not let us into the web interface so we need to rma it which needs some downtime to switch it over.
Sound like you don't need a lot of bandwidth to me. The repeatit (or similar) wireless bridge might well be a good option. For is it has been fit and forget with no hassle after 6 months.
