Please help with these TT bikes

[cbrook@harkel.co.uk]

Me and my 16 year old son were new to road cycling last year and a work colleague, noting that the bug had bit, kindly donated us two TT bikes (hopefully photos attached if uploaded sucessesfully but not very confidant). We are currently doing a bike coarse to help expand our knowlegde and contacts so we can bring these fantastic bikes back to life. The bikes were built in the 80's by JF Wilson of Sheffield, which is now run by Nigel Wilson (Jim Wilson's son). Nigel was made up to see them and happy that we were keen to bring them back to life. He was't able to date them exactly and at a price could bring them upto modern standards. I am keen to know if anyone could date them exactly and recieve advice regards the restoration. We would like to do the restore ourselves and are of a mind to keep them as original as possible. The problem with this is, that they are single chainset (52 teeth) with the 6 speed casettes ratios at 12/17, not ideal for Sheffield's hills and starting quickly at junctions. Can we change these? Where do we get the parts for a sympathetic restore?
The most complete bike is Columbus frame with the word "ACCIAIO SPECIALE" on the badge, Campag headset, chainset, seatpost and hubs, Cinelli bars (says 66-90 Campiona del mondo on them), Cinelli stem, brakes say GC on them, saddle is a turbo, cassette is shamano, rear mech Huret, Mavic open 4 wheels. The other bike is Ishiwata 017 frame, Campag chainset, seat post, hubs, Cinelli bars and stem, brakes say GC on them, saddle is a turbo, headset is a shimano 600, the casette I can't ID and there is no rear mech.
New to forums as well aqnd this is my first post, so fingers crossed.