First off, they aren't a major European chain, just a large chain in the UK. I think they account for just under 20% of cubes sold in the UK.
Another thing is, they stopped selling the GBA a few months back, reason, unknown, must have been something major though...
Though I'm pretty sure it has something to do with the following.
I'm pretty sure I heard Nintendo wont let the Dixons group sell the GBA:SP. This is because they decided not to stock the just now released modem/BB adaptor (The first console to officially go online in the UK/Europe).
It's pretty funny really, I'm wondering why they didn't wait just a week or so until Metroid Prime came out.
RE 0 just came out, and it reportedly increased the sales of the GC by quite alot. So they definately should have waited just atleast a month or two longer (Zelda comes out May 3rd).
The last 'big' game that came out here was in.... early November. And that was SFA. So one might expect the sales of the GC to be pretty damn slow.