Welcome to the world of aikido!
I must confess to some astonishment that your question unleashed a whole flood of opinions about what kind of keikogi to wear: enough material for a Ph.D. thesis.
When I started aikido in UK as a student, we all trained in tracksuits until we felt sufficiently committed to buy the appropriate kit: in my case a heavy-duty judogi. It was very good in winter but very hot in the summer and, since I trained 3 times each week, it became very sweaty and stained—stiff enough to practise all by itself without the wearer. So I also bought a lightweight karate training suit, but my pace of training (eventually several hours daily) required at least two suits of both kinds.
You asked about a heavyweight or lightweight keikogi. Well, in summer training here in Japan, it is customary for me to lose about 3 kg in the course of a good 2-hour training session and the keikogi has to absorb most of this sweat.
In my own dojo, we do not require students to wear keikogi until just before their first kyu grading (i.e., until after about 6 months of training). Of course, most students buy a keikogi immediately, but I like to allow beginning students a much longer period in which to decide whether aikido really is for them. If it is not, buying a keikogi is useless expenditure.
From your photo, your keikogi is just fine, except that the ends of your belt should not hang down vertically. They should be tucked in around your waist, after you have tied the knot.
I am curious to know who is your teacher in the UK. Please feel free to contact me by private e-mail if you think it appropriate.