During an ILS approach to Newcastle International Airport (NCL), ATC instructed the crew to conduct a go-around. This manoeuvre was mishandled and it led to a slat and flap overspeed with an associated caution message. The Quick Reference Handbook (QRH) actions in response to this message were not followed correctly. Consequently the crew assumed that they would have to make a flapless landing and they decided to divert to an airport with a longer runway. They realised they would have to use some of the final reserve fuel but, when a low fuel caution light came on, the appropriate QRH checklist was not actioned. The crew continued to try to resolve the flap problem and, despite straying from the QRH instructions, they did ultimately regain normal flap control. When the aircraft arrived on stand at Manchester Airport (MAN), the total fuel was 700 kg below the final reserve figure and there was an imbalance of 500 kg between the tanks.