I think you have made a very good start, each brew will improve as you learn from mistakes, but better if you can learn from other peoples mistakes so I will list my early mistakes so you don't need to make them.
1) Kits use tap water, so they need to make alcohol quickly so nothing else gets going, however your brew was a little too warm, I aim at 20ðC but above 18ðC and below 22ðC for first few days is what you are looking for with most kit yeasts, stick on temperature strips are good, but give an average between ambient and brew temperature so in a room at 17ðC the strip showing 19ðC means brew at 21ðC the reverse is also true room at 21ðC and strip showing 19ðC then brew at 17ðC so they are just a rough guide. Thickness of fermenter wall will effect how accurate. Also because using tap water, you can never be 100% sure of no infection you will get the odd infection what ever you do, but rare, but also means although things need to be clean, no point in going OTT as your only using tap water. Using a sensor held against the side of fermenter under something to insulate it from ambient air, I use a sponge, will give you a much more accurate reading, it was when I started to do this that I realised about stick on strip being an average.
2) The air lock can help to see when fermenting is over, however I had to use electrical stuffing glands to stop them leaking and my fermenter has a screw lid so easy to seal, after all the work in sealing the air lock, now I don't use one, I now brew in a freezer with temperature control so a bung is enough on lid mainly as not enough height for air lock, and the stick on strip does nothing as I can't see it with freezer door closed, just use reading on the STC-1000.
3) Time to bottle needs the hydrometer to see if finished, but once you have temperature control air locks and hydrometers are only a second safety check, the brews all take same time as temperature constant so I know 20 days start to bottling for most kits. But before temperature control I have had a brew still active after 40 days, 40 pints takes a lot of heating and a lot of cooling so in my kitchen in winter central heating only runs during the day, so day time 20ðC but night time 16ðC as a result brew around 18ðC since fermenting gives out heat at start it was around 19ðC ideal, but as the fermenting reduces and so heat from fermenting also reduces the brew would be at 18ðC which is just a little too cool, it did not stop, but was very slow.
I tried using an old demo underfloor heating tile 18W to warm up my brew in winter, however it was too big, so I would return to find the brew at 26ðC or higher, hind sight is easy, needs around 8W in a fridge switched off outside to maintain 20ðC in heart of winter, weight of heater matters, with my tile after switching off it took time to cool, so would over heat a little, using a simple 8W bulb very little weight so less over shoot, no need for huge heaters. Likely the best heater is the fish tank heater in the brew, however cleaning is a problem, better if not actually in beer, putting fermenter in a trug with water and heater not perfect but well on the way.
Problem with fridge was insulation too good, so starting a new brew at 19ðC with ambient at over 12ðC and brew would hit around 22 to 24ðC then cool down again, so likely in your summer house in winter a trug with a fish tank heater and a body warmer with air lock out of neck will keep the brew within reason during cooler months.
I find if it starts at 19ðC and first 3 days are cool enough to stop it over shooting then after that even if it hits 28ðC it is not too bad, it is first 3 days that counts.
Now I use a fridge/freezer in freezer both heating and cooling in fridge only heating, so first 5 days in freezer, after 5 days I can move to fridge with only heating, actually move around day 7.
I found the kits vary with what you can do with them, Yorkshire bitter add any extra sugar and far too bitter, Scottish heavy however you can near double sugar and still OK. Having said that the two can kits are far better taste than any one can kit. However temperature matters, so again Yorkshire bitter if it gets too warm far too bitter, Scottish heavy will get away with it better, and the Coopers range seem to stand much more heat.
Since too hot seems to alter taste very like too much sugar in early days I could not work out a happy medium as temperature was not constant. Latter I started the other direction will low alcohol as it means I can drink more, however low alcohol means does not keep as well and more likely get an infection. Around 3% seems OK.
But main thing is enjoy.
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