Flagship store on Regent Street, just down and across from Hamleys I think. One in Brent Cross too.
Actually quite a few in the UK
http://www.apple.com/uk/retail/storelist/Birmingham, Bullring
Level 3, Upper Mall West
Bullring Shopping Centre
Birmingham
B5 4BU
0121 260 1900
Essex, Lakeside
Unit 245, West Thurrock Way
Lakeside Shopping Centre
Grays, Essex
RM20 2ZP
0170 871 7500
Glasgow, Buchanan Street
147 Buchanan Street
Glasgow
G1 2JX
0141 300 4950
Kent, Bluewater
Unit 132, Upper Mall
Bluewater Shopping Centre
Greenhithe, Kent
DA9 9ST
01322 640100
Kingston, Bentall Centre
The Bentall Centre
Wood Street
Kingston upon Thames
KT1 1TR
0208 213 2020
London, Brent Cross
Unit V6a, Upper West Mall
Brent Cross Shopping Centre
London
NW4 3FP
020 8359 1050
London, Regent Street
235 Regent Street
London
W1B 2EL
020 7153 9000
Manchester, Arndale Centre
U23 New Cannon Street Mall
Arndale Centre
Manchester
M4 3AJ
0161 216 4570
Manchester, Trafford Centre
146 Peel Avenue
Trafford Centre
Manchester
M17 8BL
0161 240 1000
Sheffield, Meadowhall
80 High Street
Meadowhall Shopping Centre
Sheffield
S9 1EN
0114 212 1000
Solihull, Touchwood Centre
Crescent Arcade, Unit SU16
Touchwood Centre
Solihull
B91 3GJ
0121 224 1300
Southampton, WestQuay
Unit SU35, Upper Shopping
WestQuay Shopping Centre
Southampton