I know its not a DS/PSP, but the GBA SP is still a great handheld, that is still used by lots of people (my kids both have one). IMO this console is much better than the Gameboy Micro, as it offers backwards compatibility and the clamshell design means that the screen stays protected when it is shut.
This seems a great price for someone wanting to pick up a cheap first handheld, and there are literally hundreds of great games available from the GB/GBA back catalogues..............
Price after Quidco is about £29 - for a limited edition SP & Mario game - nice!
If you can get your basket to over £30, then you can also use the £3 off voucher - feboffer