Can I win more at my current level (38%) or should I move up

The answer depends on the average buy-in of these SnGs. If this is at $5 SnGs or lower, it might be more profitable to move up, but if you're doing this well at like $20 or higher, I'd recommend sticking with the level you're at, at least for a while. And when you say average profit of 38%, I assume you mean that's your Return On Investment (ROI)% right?

A 38% ROI is very good at any level and pretty close to the maximum you can expect. I think as high as 45-50% is potentially sustainable, although a lot of people don't; I think it can be if you're at the right site, consistently playing with the "right type" of players. The play at Party Poker was so perfect for me, I could sustain a 50% ROI in $20 SnGs over several months, but I seem to have no hope of anything nearly that lofty at Full Tilt.

Thank you yes I mean return on investment playing at £5 and £10 games.

38% is a very good number. Playing at the same sort of buy-in levels, my ROI floats around between 30 and 35, and I had been well content with that (until I read your post ).

You could try moving up a level. Alternatively (and this is my approach), regard your SNG winnings as your basic income and look for a little "overtime" by re-investing some of it in the odd cash game or MTT, looking for a big score. The variety helps to keep you sharp and I find that playing an MTT is fun when you know that your entry was free because you won it in another game. If you lose, there`s no harm done, and if you win it`s a nice bonus.

BTW, you have affiliate links in your signature. That`s against forum rules. I would change it before the mods catch up with you.