F0.7 Nikkor L series prime woteva because the kit lens was just as good and you're basically paying for the fancy colour.
Which is equally a valid point for many many situations and if you read any of my posts you will see that I apply the same type of recommendations to camera kit (have been though pro FF kit and now using m43).
However, the OP was helpful enough to describe the use scenario and a trip to the Farne Islands in May is hardly Everest base camp.
I've done my fair amount of reasonably hard trekking (e.g. Kilimanjaro, NZ trails, Sapa, Machu Picchu etc) and I've owned an awful lot of different gear and, as with camera gear, it's about knowing what is appropriate for a given situation. For example Machu Picchu is fine in trainers, Kili needs serious hiking boots and good down insulation for the summit (it was -17 when we were there - see my avatar!).
I can tell you that in my experience in all but extreme situations kit that fits well is far more important that a brand or 'special' performance gear - the law of diminishing returns starts far lower than lots of people are made to believe by advertising. Just as with camera gear.
This doesn't mean I don't have good kit but I am aware that it isn't generally necessary, as with 99% of people and their camera gear.
I also do a lot of running (5 marathons so far, countless halfs) and cycling (London - Edinburgh in 4 days) and again, the Decathlon kit has outperformed some of my much more expensive branded kit for half the cost. I am fortunate enough to live near a Decathlon store and now I am past the brand snobbery it is always my first port of call for any 'sports' gear, I don't always buy it from there but it is always worth a look.
edit: Just to add, one of my favourite out-doors things is a pack-kagool and I use it for travelling in Asia as it is handy for the on-off showers you tend to get and stuffs into itself into a nice small package so fits in a bag easily. It is lightly rubberised internally so not the most breathable but is big enough to move freely in (so tend not to boil in the bag), has taped seems, a good hood and so far been 100% waterproof (including a recent visit to Hong Kong where I wore if for around 8 hours in heavy rain). Best thing is that it cost £6.99 in Decathlon.
I also have an expensive Goretex jobbie which I love and use a lot but it just isn't necessary a lot of the time and not so handy for travel.
Edit 2: It's only £5.99 now
https://www.decathlon.co.uk/raincut-mens-waterproof-jacket-black-id_8300326.html