While the mix of miniatures is basically a mirror of the German forces (the same number of MG, bombardiers, etc), the poses are different. In particular, the poms have bayonets fitted ready to go over the top and get stuck into the hun.
Based in the same way and otherwise with a similar palette, the two sets will look OK together on the board.
There is an extension focused on tanks on Kickstarter at the moment. It is good value and the models look like they will be the same high standard. But, you read it here first folks, I’m declaring my first world war collection finished. Given the number of other projects I have on the go, I’m content with the base set.