Professor Simon Hix studied the UK's influence in the EUropean Union in 2015 and concluded-
These network pictures clearly show the centrality of the UK in EU negotiations. Germany and France are also close to the centre, but UK officials appear to be the best connected of all the member states’ officials.
In other words, when it comes to negotiations behind the scenes, before votes take place and before laws are adopted, the data suggest that the UK government is right at the heart of EU policy-making, and certainly at the top table, alongside Germany and France. The data also suggest that the Eurozone crisis has not had any noticeable effect on the centrality of the UK in EU bargaining.