Hi there
I dont know what the spa treatment contains but it sounds a little bit on the expensive side. I have a few tips for you...
You should be looking for commercial products with something called "salicylic acid" in them. It acts in several ways - it decreases inflammation (it's basically the same ingredient as in asprin), and it exfoliates and regenerates the cells. It also keeps the pores open so they dont block up with sebum. L'oreal do a product aimed mainly at women but it's got a good high concentration of salicylic acid in it. I'll find out what it's called and post it to you.
Also, your son shouldn't use anything too abrasive (i.e. soap bars or alcohol based cleansers). Stuff like clearasil only increases 'rebound' oil production because it strips the skin of all the oil. So use the most gentle cleanser you can find. Liz Earle do a soap free shower gel for gents which is not cheap but makes a great, gentle facial wash.
Tea tree oil is a natural antibiotic which can be dabbed directly onto spots - Australian Body Care sell a high quality version.
Also, Witch Hazel liquid, which can be bought from most small pharmacies is useful. You just dab onto the affected areas with cotton wool. Doesn't smell great, but it's cheap and it works.
One other thing, get him a some supplements. Firstly, Vitamin A supplement. The retinol is great for treating acne. And also some Omega 3 supplements.
If all else fails, you can get the Dr to prescribe an antibiotic or a very strong prescription only form of Vitamin A. I'd keep this as a last resort though.