The UKBA published an extended list of approved English language tests suitable for Tier 4 General Student visa applications. This should mainly affect students studying language courses rather than University programmes.
The Secure English Language Tests (SELT) are listed below in this text taken from the UKBA website:
‘The UK Border Agency accepts tests provided by the following organisations for use as evidence of proficiency in English Language.
Cambridge ESOL
City and Guilds
Edexcel
Educational Testing Service (ETS)
Trinity College London’
For full details see this document on the UKBA website.