score:6
It sounds to me like your Quecha jacket should do the job - the main advantage of more expensive fabrics is improved breathability etc - it's ppossible for quite cheap materials to be very waterproof. Although investigate the zips - if they're not sealed/taped then water will ingress through them in sustained rain.
Be aware that in the hills of the UK, the weather can change very quickly. A sunny and warm day at the base of the hill may turn to a 10m visibility, rain soaked slog by 3/4 of the way up. Ensure you have good navigational equipment (map, compass/GPS) and warm, dry clothing with you at all times. If you can let someone from your accomodation (if any) know the route you are planning on going before you leave, all the better.
If you're determined to go out in all weathers and cover some distance, investigate some waterproof trousers as well. When the wind comes up, or you're walking through the cloud, the rain drenches you all over.
You're sensible to be prepared - October is one of the rainier months