A pretty simple deal this one. Argos are currently offering 4200 MSP for under £30, which is quite frankly a bit of a no-brainer. If you've been waiting for the Summer of Arcade to kick off before buying up a load of points to spend on some utterly cracking games then this is the deal for you. You'll be hard pressed to find a better price than this one.
Incidentally, you might also be interested to know that Argos are only charging £14.99 for 2100 MSP. It's not quite as economic and buying double that, and 7dayshop have had them at this price for some time, but if you don't want to blow all your money at once then it might be the logical choice for the frugal gamer. You can buy 2100 MSP for £14.99 by clicking here.
Assorted tips oft he hat go to ChrisPalmer, TaylorUk and empwan at HUKD