HMV have "Mercury Meltdown Remix" for the PS2 back on offer for £2.00 (inc Del.)
You can also get cashback through the usual sites (e.g. 5% Quidco, making it £1.90)
Next best price is £7.99 from ShopTo.
Please be aware that it is listed as "despatched within 14 days", and when they last had it at this price, some people ended up having their orders cancelled. However, at this price it's gotta be worth a punt, especially as you have nothing to lose. :-)
Take control of a liquid Mercury 'blob', and avoid the various obstacles and hazards to reach the end goal. The Mercury blob itself now has 4 varying 'states' Normal, Solid, Fast and Slow. These states allow for larger more complex levels, which in turn mean a greater challenge and more enjoyment.
Featuring a total of 12 labs (two of which are exclusive to the PlayStation 2 version), 'Mercury Meltdown Remix' offers a massive 200+ levels, more than any previous Mercury title.