White Spot

I have just suffered a break out of white spot in my tank and I thought I'd ask if you think I am treating it in the correct way. I have changed 20ltrs of water right away its a 20 UK gallon tank> I gave the filter medai a good clean and then treated the water with a anti white spot cure as directed I also put the temp of the tank up to around 85-88f. I think about 6 fish are effected at the moment two clown loaches and around 6-8 of my neon tetras. All others seem ok at last check. The treatment says it will only become effective when the spores from the disease are free swimming not when they are on the fish itself. DOes this mean that the fish will ultimately die. I have had my two loaches for around 2 years now and they were very good specimens I will be really sorry to see them go. I think the whole disease started when I added a new bunch of neon tetras to the tank around 10 days ago. What surprises me is he fact it has taken so long to surface. I chg the water and clean gravel ect freqeuntly so I dont suspect any issues with my water quality so the only other thing could be these new fish?
Hopefully someone can give any more guidance or if the worst comes to the worst let me know if the fish that already have it are going to die I think I would rather know.
Also I do not have another tank in which to trf the diseased fish to so unfortunetly that was not an option

Thanks I understand that you should but in any case this was around 10 days ago these fish were introduced I didnt think it would take that long for a breakout of ich to take place surely this would have happened a lot sooner had they been carrying the disease?

I am using a medication for White Spot but as I am in the UK it may not be avaliable in the US but I presume the are all pretty similar. Anyway I have added it last night and it says it will stay effective in the tank for a "couple" very technical eh? days. However my next question is do I go home tonght and change some of the water or let the disease run ots course and hope the medication kicks in before it spreads?

thankyou for your replies it sounds like I seem to be doing most things correctly i.e add medication, increase temp as far as the making them comfartbale goes I have left everything in the tank as it is for a while anyway beacuse as I mentioned the Clown Loaches are not new, this includes all their normal plants hiding places ect.
One more thing if you dont mind is do the fish ever fully recover from ich once they have actauly got all the symptoms I know CL's do get it worse than most fish as they are scale-less and mine are pretty badly effected more so than the noens?

Oh Dear! I don't think I can hold out much hope for them then. This is what happens when you buy fish from a bad supplier. As I mentioned it was when I bought the neons I think this has all came about and I purchased them from a place in the UK called homebase which is is kind of like your Wallmart with a reputation to match. The only reason I bought from them was because the neons they had in stock were larger than normal and I already had 4 bigger then normal ones myself. That will teach me I suppose to buy from only reputable dealers what annotys me even more is that its not something I would ever encourage anyone to do anyway yet I did it myself
Thanks once agin for all your advice I may make a little psoting in a couple of days to let you know the outcome