Man's bicycle - restoration project (Sharmans Cross B91)

Peugeot 5 speed derailleur gears - bought new 1976. Drop handle bars. Wheels 27" x 1¼" (road wheels rather than narrow sports wheels). Some rust. Problem: repeated punctures on the side of the back tyre - not the part which comes into contact with the road - and I couldn't find the cause. Has been in shed for many years. Probably a significant project. (I'm aware of The Bike Project but, from their website, I suspect the required work is too extensive for them.)