The OEM brakes shouldn't judder at high speed, there's something wrong - 99% of judder is DTV (Disc Thickness Variation) caused by either uneven disc wear (extended cruising without using the brakes can exaggerate this, constantly wearing the high point as it wipes past the pad making thin spots which is felt as judder when the brakes are used) or uneven friction material transfer causing high spots.
Either way new discs and pads should cure this.
Those are expensive! £300 for a pair of cast iron discs!
That's similar to the OEM discs prices - and the OEM discs are better quality (tighter machining tolerance and probably a better alloyed HC cast iron grade).
Don't get drilled discs - only reason is for looks. They have worse performance (each hole is a stress riser) and more chance of brake noise.
For a road car - the best brakes overall will be the OEM brakes. They go through way more testing than any aftermarket brakes.
To save some money, any aftermarket coated discs (not black paint like TRW) with R90 & high carbon (R90 provides a minimum reasonable quality) will be reasonable.