Please book an On-Site appointment, for this sort of bike, I would normally recommend replacing the gear cables (£20 set), brake cables (£15 set), brake blocks (£7.50) and inner tubes £6 each). The time taken would be approx. 30-45mins.
If you chain is badly rusted, or the wheels have rusted or broken spokes, the bike may not be economic to repair.
I do not believe in just oiling cables to make them better – as you will be calling me in a week or so because the gears or brakes are not working again. The rubber in the brake blocks and innertubes perishes over time, hence replacing these.