Test centres are located in major cities throught the UK, and the current cost (September 07) is £95

more information on the ielts test is available by filling in a free assessment

Centres are at

University of Liverpool
University of Wales - Aberystwyth
University of Bath
Belfast, Queen's University,
Birmingham, Aston University
Bournemouth, Richard Language College
University of Bristol
Cambridge, Anglia Ruskin University
Canterbury, Chaucer College
Cardiff University
Coventry, City College
Eastbourne, Sussex Downs College
Edinburgh,Basil Paterson College
Essex, Colchester English Study Centre
University of Glasgow
Guildford, University of Surrey
Harrogate Language Academy
London, Middlesex University
London, University of Westminster
London, Eurocentres
London,International House London
London, Southwark College
University of Manchester - Language Centre
Norwich, (Sub Centre of Anglia Ruskin University in Norwich)
University of Nottingham
Oxford, King's School
Plymouth, Mayflower College of English
Portsmouth, Language Specialists International
Rugby, Warwickshire College
Sheffield Hallam University
University of Southampton
Sunderland, City of Sunderland College
York, Melton College

a full list of centres with the next available dates is at http://www.ielts.org/test_centre_search/search_results.aspx