Carbolite 103 is not the model, that is the grade (low end) of tubing used. No idea on England market. Bike is NOT in what I call ready to ride condition. Needs bar tape and lever hoods, new tires, and given those items, I would assume it is going to need new bearings, grease, cables and possibly housings.
Single speed conversion? If so, that is about the lousiest SS conversion I have seen. Still has the rear derailleur hanging out in space, still has double crankset, looks like the shift cable was cut about 2 inches below the lever bosses. I would pass around here.