360 sold more than the Wii in the UK I think. Unless DS counts I don't think Nintendo have ever been number 1 in the UK. Maybe that'll change in like 20 years time with the new generation of kids.
Correct however 360 caught up Wii around June 2013, Wii was the (home) market leader for years.
What I mean by this is that in the end both Xbox 360 and Wii sold in absolute term so well that they are respectively the third and fourth best selling console ever in UK and the gap between the two is (relatively) small.
Something very similar happened in US (which of course is a bigger market than UK).
DS: 12.3M (as December 2010)
PS2: 10.0M (as January 2010)
XB360: 9.0M (as June 2015)
Wii: over 8.4M (as June 2013)
PS1: 7.2M (as December 2005)
GB/C: 6.6M (as December 2005, GBC only 1.5M as December 1999)
PS3: 5.9M (as June 2015)
GBA: 4.6M (as December 2005, GBA SP 2.38M as December 2005)
PSP: 3.6M (as January 2010)
XB: 2.1M (as December 2005)
N64: 1.6M (as December 2001)
GC: 1.2M (as December 2005)
DC: 0.28M (as May 2000)
Source: Chart-Track