What about the size? Ultra portable or as big as possible?
Tbh though, you can get decent i3, 4GB RAM laptops for around £400 nowadays, just toss in another 100 for a 250GB SSD and you'll be more than happy. I have one of those specced laptops (well, still have to get an SSD for it but even with the mechanical HDD it's alright), and it's perfect, even does a bit of PhotoShop. Only downside is that it's originally a budget laptop so the casing/shell is plastic-y and not great (Toshiba).
Something from the Dell Inspiron 15 3000 line-up would probably be alright.
http://www.dell.com/us/p/inspiron-15-3542-laptop/pd.aspx?c=us&cs=19&l=en&s=dhs&~ck=mn
Or if you want to go for a bit more quality all-round, the Inspiron 14 5000:
http://www.dell.com/us/p/inspiron-14-5447-laptop/pd?oc=fncwl2514b&model_id=inspiron-14-5447-laptop
Could also have a look at the PCSpecialist website and see what kind of configurations you can come up with.