Hi Scott,
For the size problem, you might check yourmoodle/filter/tex/pix.php line 61. Depending on your Moodle version the line number might be off one or two, but look for '\Large ' and change it as desired and see if that fixes the problem.
As for the £ problem, have you just tried typing the £ character? \mathbf{£} $$\mathbf{£}$$
Every font I have looked at, includes it, so it should just work.
Thanks for getting back to me. I'm not in a position to delve into the code, and I don't think the LaTeX on the site is fully installed as I've tried lots of things from the web that don't want to work on the moodle I am subjected to have to use.
I tried \mathbf{£} and just got [?][?]. Never mind. I don't need it desperately.
How about create your LaTex with the equation editor, with everything except the £. Once you finish with the equation editor and you are back in the Atto editor, click where you want the £ to be and use the Insert Character tool (Ω) to type the £ there. This method works on my system.