Beige chinos are always a winner with navy blazer. White chinos are perfect with blazer, but obviously a disaster waiting to happen in a club. I'm also partial to a burgundy chino. If you're less confident with that wear a slim pair of indigo jeans.
Shoes wise, I stick with the ever classic tan brogues and a matching belt. There's some on ASOS, full leather all over, and only 50 quid.
If you're looking to accessorise, what about a burgundy knitted tie (there's one in NEXT for a tenner), or a white pocket square (ignore the purists, you can pick one up in Primark for like 50p)