SVP have some Mediastar discs. Their blurb says: "Mediastar aren't yet widely known in the UK. These unbranded silver topped discs are manufactured using a high-quality Taiyo Yuden dye. Supplied in unbranded packs of 100 discs."
The normal customer price is £13.99, but if you make an SVP account and follow the instructions at http://svp.co.uk/hukd.php
then you'll get special discounts on all items, and these are brought down to just £9.99. That's 10p per disc!!
Delivery to UK mainland, via courier, is £5.86... but this doesn't increase with your order so you may want to buy a few or have browse around to see if you can spot any other bargains. There's usually plenty.