Hi Vicki,
I think you have written up a taller order than usually gets answered at one time in the forum. I'm probably not up to the task but will throw in a few things... I think beginners to the hobby (not really knowing if you are that!) often divide up at this early stage, some buying a kit at the LFS without really thinking about it, their focus being on the fish they want to pick out - others split the other way and do a lot of research on individual hardware items.
If you fall in the latter half and your question is about the physical tank itself (it appears it is) then you might be the researching type and I recommend that you will find any number of older threads here by searching on "best tank" and other such strings. There are a number of suppliers in the UK and various members have commented on them. Having had a tank break only a few months in, I can say that smooth stands and strong tanks are definately an important thing!
In the UK there are a number of good kit-makers and I'm sure some of the members will be willing to advise there. It can be more daunting to approach each of the major bits of equipment separately when all of it is new but if you have that energy and can take the time you would usually find that you are rewarded with perhaps an even better setup.
I would place the filter in top position and the piece of equipment deserving most focus, by far this thing makes a bigger difference and is the subject of much of your later attention. The tank and stand of course are important and then the lighting has a number of things to think about. Heaters and thermometers are relatively easy.
Tank size (couple of rough quick thoughts)
If you get the members started on this you will quickly see that they are very concerned that newcomers understand that a larger tank is better for a beginner because a larger volume of water is more stable and the pseudo-environment it creates is more forgiving of beginner mistakes - it takes a little longer for the mistakes to have dire effects. If you press this topic a bit though, you will also find that you can get the members (perhaps reluctantly sometimes) to admit that there are some harder things about great big tanks.
Prior to thinking about tank size you must of course think about the money involved - it often gets quite a bit more expensive than people expect. You must evaluate the potential spaces in your home and the weight involved. You need a place out of direct sunlight that is nice for tank viewing but not in a high traffic area where people are moving or carrying things about that might hit the tank or scare the fish. It needs to be not too effected by heating and air conditioning or very cold windows or such. There are articles that get even more picky on this topic.
Very large tanks are difficult to transport, difficult to place and they are extremely heavy, requiring thought about floor reinforcement. They require more equipment and electricity. But as mentioned they are easier to keep stable with respect to water chemistry. Tanks under 20 gallons begin to be trickier to keep stable as the size gets smaller. This makes 20 gallons an often recommended sweet spot for many beginner recommendations. There are many nice shapes in the 30, 40 and 50 gallon vicinities as you grow a little more ambitious. As tanks get bigger, things to think about are that they require more bags of heavy substrate that must be washed and moved. As the walls get higher it can get more difficult to get your arms down to the substrate to work. Water changes become a bigger and more time consuming chore. More fish, food and supplies are needed. But of course, in the end, big tanks a indeed glorious and most of us wouldn't be in the hobby if we didn't dream of these.
Anyway, good luck! I see many chats on here about "Jewells?" and "Rekords?" and other UK kits I know nothing about but I'm sure the many UK members will help you out about these!
~~waterdrop~~
would buy another if needed a 20g kit.
