Hello; I almost always have planted tanks going and have for a few decades. Never have used CO2 so cannot say much about it other than it is not needed. CO2 might be neat to try but my take is maybe not when you are just starting.
I have found for rooted plants the substrate of four to six or more inches deep works well. I stopped using sand many years ago. The fine sand packs and in my experience plants did not do well. There is a way to use sand that can work but is a chore to get enough of the right sized particles. I will not go into this unless you ask.
One more things about sand, especially the finer sands. It packs if very deep and can form anaerobic pockets of toxic gas. Since I prefer deep substrate this is a problem for my use.
Lighting has not been a big issue in my experience. I started keeping planted tanks back in 1959 and have grown plants under most types of lights starting with incandescent bulbs to LEDs currently. Note- not the somewhat expensive LED lights I see for sale in fish shops, but off the shelf LED types found in big box stores I use in old modified hoods. I do not spend money on expensive stuff if cheaper stuff works, and it can.
I will try to add a picture of a 55 gallon tank under a $30 LED shop light.
Hello; This is the 55 gallon a couple of years ago. I found a 48 inch LED shop light on sale at Wal-Mart and stuck it on top the tank just to see how it did . I left it on and the plants started overrunning. It is not at the color spectrum I like but is close enough. If you look close you might see a couple of young angel fish. I already had a hood with fluorescent bulbs but this light has done well for a few years. I think it is around 4000 to 5000 K. I like the 65000K range of the color spectrum better but this works well enough.
Too bad you are in England. I remove plants from time to time and have a bucket of plants I took out recently you could have. I usually take them to a fish shop but it is 70 miles away and with the virus I do not go so much any more.