Old Spice, a classic that everybody should try out, usually available around £7.
Nivea 2 Phase, nice enough fragrance but not long lasting. But (that's) not what it's about, it's an excellent A/S with a moisturiser built in. Check out Superdrug for regular special offers, like 2 for 1 or whatever.
+1 for the Nivea Phase 2. They won't smell as sophisticated as the DR Harris but the La Toja and Speick aftershaves are less than half the price of the DR Harris; and outperform it in terms of perfomance, in my view.
Boots and Superdrug own brands are actually rather good, including Boots Bay Rum hair tonic which can be used as an aftershave too! All very reasonably priced for your budget.
Likewise, look for offers in Superdrug for Nivea 2 Phase aftershave. Again very well priced and you'll see this used in a lot of SOTDs.
Superdrug may still have the "Bespoke" Eau de Parum range in store. There are 4 flavours and it was buy 1 get one free (£5 each for 100ml) a few weeks back. They're all pretty pleasant esp the Citrus and Vetiver.