This is what SE support told me when I asked a similar question.

Dear Sir/Madam,

Thank you for contacting the Sony Ericsson Customer Care Centre.

Regarding your enquiry,  I have taken the liberty of listing below the
location details of your nearest service centre where your product can be
inspected and repaired under the terms of your product warranty:

Premiere Eurocom Ltd
Unit 9
Advanced Business Units
Waterside Drive
Langley Business Park
Langley
Berkshire
SL3 6EZ

Tel : 01753 543 712

Yendell Communications
81 Station Road
Addlestone
Surrey
KT15 2AR

Tel : 01932 850202

Intec Cellular Ltd
Hillside
50 Moxon Street
Barnet
Herts
EN5 5TS

Tel : 0208 216 3896

R's Electrics
815-817 High Road
Tottenham
London
N17 8ER

Tel : 08707 746 333

Phone Centre
855 Forrest Road
Walthamstow
London
E17 4AT

Tel : 0208 923 9991

Fleet Communications
196-200 High Road
Chadwell Heath
Essex
RM6 6LU

Tel : 0208 597 2000

Fleet Communications
77 Avery Hill
New Eltham
London
SE9 2BJ

Tel : 0208 2942000

Please contact the service centre in advance in-order to arrange a suitable
time to visit the service centre. The service centre will be able to offer
any further directions and also the opening and closing times.

Please remove your SIM card. If you have more than 99 numbers stored on the
card they will actually be stored on the handset and as a result we would
recommend that you make a brief note of the numbers.

Please also take with you some form of proof of purchase for the handset.

If the service centre is not convenient to visit, you can send the handset
directly to a company called Celestica. The relevant details are found
below:

Celestica (Telford) Ltd.,
PO Box 80,
Oakengates,
Telford,
Shropshire.
TF2 9WT.

Telephone number: 01952 230 402
Fax Number: 01952 237 278
E-mail: EndUser@celestica.com

The handset should be adequately packaged and sent special delivery. Please
remove SIM card. The following documentation should be sent with the
handset: your name and contact details, contact number and e-mail address if
available. Please take note of the handset model and the IMEI number prior
to sending the unit to Celestica. Please send a copy of proof of purchase.
The turnaround time is 10 working days from receipt of the handset at
Celestica.

Please contact the Sony Ericsson Customer Care Centre again if we can assist
you further.

Kind Regards,
Mark Conniff

Sony Ericsson Customer Care Centre
mailto:questions.gb@support.sonyericsson.com
http://www.sonyericsson.com