A superbly illustrated key to the Chrysididae of the Nordic and Baltic countries (in English) is available as a free download. It should provide a very useful aid to identifying wasps in the family Chrysididae. The key includes all the British mainland species apart from Chrysis rutiliventris* . It can be downloaded here
* C. vanlithi - treated as a subspecies of C. rutiliventris by some authors - is included in the key.