True, I'ev done fair amount but I used to have a colour enlarger so I didnt need the filters, I wasnt sure how much the half stops are used.If you think you're likely to get into printing, yes, and honestly, the £20 is a tiny cost relative to the overall cost of shooting and darkroom printing film. Once you've got familiar with the process and tuned into what they do, there's a fair jump in contrast between the grades, especially as you get into the 3-5 region. The slight caveat is if you were only split printing, when you'll probably find you only really use 0, 1 & 5.
I went for the full kit in the end. I think you were right, for the sake £20 having the extra filters can only be a good thing.If you're happy with additional contrast then the student kit may be sufficient for you. I hardly ever use 1/2 grades split printing (I prefer to start with finding a time for 0, then overlay the 5s rather than halving a 2.5 time), but use the 3.5 for single grade prints dodged & burned regularly. Fwiw, I print colour too and have a colour head but still use under the lens ilford filters for bw. One nice thing is they're density balanced so in theory if you change the grade it doesnt effect the exposure, and theyre much quicker to change back and forth with splits.