choosing my first greenhouse, help!

[Lia23]

Hi everyone!
I've decided to buy my first greenhouse and still cannot decide on material. Just a brief description of my situation so you can easily understand my needs. I will be growing intermediate and warm temperature orchids in there and I live in the UK (the temperatures didn't drop below -5 for the last 3 years). The size of the greenhouse I can put in my small garden is 2x2 meters (I guess it's approx. 6x6ft). There is a concrete base in the garden, so I do not know what base I should get for the greenhouse or I do not even need one?
Also, materials!!! is my main concern
I am deciding between toughened glass and polycarbonate sheets. First of all it looks like polycarbonate hold more heat than glass which is good and also it protects from sunburns (harmful UV).
However, toughened glass looks much more attractive (well on pictures, haven't seen in real life). What would you choose?
I've attached two types of them so you can look and have an idea. First one is polycarbonate that is 4mm thick Lacewing™ 6ft x 6ft Deluxe Black Aluminium Frame Greenhouse £222.99
Second one is toughened glass which is 3mm thick
Lacewing™ 6ft x 6ft Deluxe Aluminium Frame Greenhouse with Toughened Glass £271.99

OR this one 3000s polycarbonate with a twin wall at the top... BillyOh 3000S Easy Fit Aluminium Silver Greenhouse with Base and Opening Vent - Greenhouses - Garden Buildings Direct

Please give me your opinions on those 3.