When I tried the Fab Filter plugins I was surprised how small the GUIS are.

Do they resize larger?

No, they don't. Pro-L offers "normal" and "compact" sizes, with the latter hiding the graphical display. Pro-Q and Pro-C don't have any resizing features. All of their plugins that support modulation allow you to hide the modulation routing section, reducing the size of the UI. Saturn has "wide" and "normal" sizes, which is only helpful if you have it split into many bands.

My eyesight is poor and there are many plugins that I've had to use a screen magnifier with, at least until I've learned where all the controls are. However, the FabFilter plugins aren't among the ones I have trouble with. I don't have any trouble reading them, probably because the labels are white text on a dark gray background, and they don't waste screen real-estate with photo-realistic knobs so the control density is reasonable.
For those who are more severely impaired visually than I am, I'd recommend Voxengo GlissEQ, which has three size options, the largest of which is huge.

Forgot to mention this earlier.  Do you teach music by any chance ... or are you a student?  You can get a one-year 50% discount deal if so.  What you buy cannot be resold, but the high quality of FF software is such that you're not likely to want to sell it anyway.

When it comes to EQ's I've always wanted an EQ where you could maximise the GUI to full screen. 

50% discount. Hmm.. I'm not a student but my partner is. But how do you prove that you are a student when buying? And is that something that only works if you live in the states? I live in Sweden.

/M

see http://www.fabfilter.com/.op/educational-discounts for details

I'll bet those fake-passport folks in Nigeria could fix you up with a student ID card.

Of course, that would entail sending your credit card number to them. But given that most of them are royalty and multi-millionaires already I'm sure they'd be completely trustworthy.