In reply to mmmhumous: Thread gear is rare for Scotland. And I'd be wary of advice to aim around 16-19. Often in the UK 10-13 is all the ice you've got to play with. Yes, keep some long ones for the belay with nice stances but figure on finding the short screws pretty handy. A protruding long screw tied off with a clove hitch is fundamentally weaker than a short one buried to the hilt/handle. I have two of each at 10, 13, 16, and a couple of long ones. Would then figure on taking 4-8 on the climb depending on conditions. In your budget I'd go:
1 x 10
2 x 13
2 x 16
1 x 19
And rely on rock gear for most of the belay.
Yes, I know that's 6 but you should find a bargain at this time of year. I bought three Petal Laser Sonics new for £25 each this Spring. They are very good to place and outstanding value if you can find them anywhere near that price.