Asos has a lot of nice stuff but a lot of it sucks too. I bought the premium membership for 1 Year and I get discounts, early access to sales and next day delivery all the time for £10 which was really worth it.
Topman and River Island are TRASH. The quality

I use Topman occasionally if I have my student ID number but most of their stuff is tacky.
Zara has some nice stuff but don't buy anything now until the sales start. I wouldn't stray far from their basic stuff or the occasional knitwear as the other stuff tends to be very overpriced (£45 for ripped jeans? GTFO

)