There are three reasons to select a kit, one it's an old favourite, two it's on offer and much cheaper than normal, and three suited to climate.
I find the Youngs Scottish heavy is slightly better than the Geordie Scottish heavy, but there is very little in it. Following instructions the Youngs has 1.5 kg of sugar and Geordie 1 kg of sugar so using same sugar in both the Youngs is slightly less bitter. Using dried malt extract or a mixture of brewing sugar and dried malt extract is claimed to improve the pint, however I was rather disappointed in the results using brew enhancer all it seemed to do was raise the price. And using dried malt extract the kit costs the same as a two can kit so may as well just get a two can kit, rather than bother with dried malt.
The last point at the moment 3 am in the morning I am looking at 18.8ðC likely in North Wales tomorrow we will have a warm day and unless I was to use a yeast selected for high temperatures I will need to use refrigeration to stop off after tastes creeping in. Time helps, but they never completely go away. First 10 days are important for temperature after that it really does not matter, not sure of Scottish temperatures, but you are looking for most beers for an average of 18ðC for first 10 days, after that even 24ðC is not a problem. I say average as 40 pints takes a lot of heating and cooling.
In the main brewing beer needs 20ðC, but the fermentation gives off heat so 18ðC ambient temperature. Coopers kits seem to advocate a higher temperature so likely starting a kit tomorrow a Coopers kit would be better. They recommend 21ðC-27ðC (70ðF-80ðF) with UK kits 18ðC~24ðC. During winter months the UK kits better suit the temperatures we tend to set central heating at, but still may need a body warmer to keep them warm enough.
Over the years Wilko, Tesco, and Morrisons have all done cheap kits. Couple of years ago Morrisons were doing Geordie Scottish Export at less than ã7, then stopped doing beer kits, Tesco last year also did the Geordie Scottish Export cheap before Christmas seem to remember around ã8.5 order on line and collect in shop, just a couple of weeks ago Wilco was doing Coopers Stout, Larger, and English bitter at ã10 with a two can Woodfords Werry Bitter kit at ã16.
Even without being on offer the Geordie Scottish Export is just ã12. But in local brew centre Geordie and Youngs Harvest as same price so from that shop I get the Youngs Harvest Scottish Heavy, Tesco even not on offer the Youngs Harvest Scottish Heavy is ã10.50.
Yorkshire is most bitter, English in middle and Scottish heavy the least bitter of three, both Geordie and Youngs. It really is hard to tell between the two makes.
Before temperature control my biggest problem was being under temperature so what should take 30 days before being ready to drink took 60 days, and if bottled too early the pressure could build up, moving to plastic pop bottles was a great move, A mistake bottling too early and simply slack off cap and release pressure, today with using refrigeration I can set watch by when the beer is ready, but a stick on temperature strip is very handy and an air lock well sealed means less testing with hydrometer. Today I just stick the fermentor in the freezer with temperature set to 20ðC and return in 10 days to swap fermentor to reduce sediment, put in fridge set at 21ðC and after a further 10 days I bottle. But before I got the fridge/freezer it was in kitchen and every day I was monitoring its progress. I made some classic mistakes, when under temperature normally in second 10 days I would set heater and forget and then over temperature, but never poured a brew away, they may have varied in quality, but still drinkable.
Before refrigeration I would stop brewing June, July and August. Now I don't need to. You are in Scotland so I assume cooler I can only say what I did in North Wales.