They have a whole bunch of very decent offers on Samyang lenses ATM. The Samyang AF 35mm f2.8 Lens is only £144, never seen it that cheap, makes your A7 almost pocket-able its so small and light, it's decently sharp too. The 45mm and 18 are down to £259.
Good price. The manual focus version of this lens is a different optical design I believe which yields slightly sharper results (and it's cheaper). The quality control on both versions of the lens are known to be poor though (decentering). Samyang have just released an updated body design of the manual focus version however (same optical formula) which is the version I'd go for personally. Great bang for the buck. Definitely the best astrophotography lens on a budget.
I bought last year for 550 :( great lens