Try looking in the Argos catalogue they usually have a wide range
and should give you an idea of spec and prices.

I bought some NTL branded phones recently. No headset socket that I can
recall, but each of the phones had a built in speakerphone. Depending on the
nature of the "work", this might be acceptable. They're fine to just put
down on the kitchen/workshop surface and chat, provided no privacy is
required and no-one else will be annoyed in the vicinity.

Christian.