In the heart of Angel, Islington, there is lovely restaurant & bar called Fredericks which is located on the cobbled Camden Passage. Over the last few years I have photographed wedding receptions there which is ideal for both small and bigger weddings. There is the whole restaurant which is perfect for bigger wedding parties and there is also the Club Room which is a great size for smaller wedding receptions.
For travel there are lots of buses that run on the busy road of Upper Street. Also Angel and Highbury & Islington tube stations close by so it very easy to get to the venue via public transport.
Fredericks is also very close to Islington Town Hall so its perfect if you don't want to lots of travelling in-between the ceremony and the reception.