I recently changed over radiators and have noticed that I'm still leaking somehow, but it's not a visible leak. I've checked the pipes to and from the radiator to the block and it's not wet or anything. I know this because the coolant in the reservoir goes down and I have had to top it up a few times since I changed the radiator last Friday. I also changed the thermostat when I changed the radiator.

Today I noticed a bit of coolant leaking from the thermostat housing, and it was on there tight enough as it is, so I'm not sure how a few drops was leaked out.

Since changing radiators, every time I start my car, it doesn't idle that well, and when I try to take off, it won't go as far and it makes splutter like noises. It sorts itself out after a few minutes however. Not to mention a bit of white smoke pours out but that has been like that for a while now. It was been taking off fine before the radiator change, I may not have bleed out all the air correctly?

I was told to take it to a radiator specialist place but I wanted to know if anyone here knew if the problem was obvious and how I should go about fixing it. I really hope it's not a blown head gasket...

Sorry if that was too long, just trying to give as much detail as possible.

I would suspect you have a blown head gasket.....

Definetly symptoms of a head gasket fault

+1 for headgasket

Yup I'd go with head gasket, check your oil dipstick for 'caramel' colored oil (water in the oil). The new radiator probably increased pressure in the cooling system (compared to the old rad, especially if it was leaking badly) and was just enough to push through the old head gasket.

water loss combined with rough idle doesnt sound good

but i have seen an AU which was dumping all its water from the header tank, fixed by replacing thermostat & radiator cap..........

+1

The oil looks fine.

I did fear for the worst :/ I'll be getting another head hopefully soon, I'll be able to change the head gasket then, right?

The sooner the better mate, while the car might be running now it WILL get worse and, no doubt blow through completely at the worst possible time. Leaving you stranded, most likely causing more problems and in turn cost you more $$ to fix. If it were me I'd be looking for alternative transport 'till you swap the heads, or replace the gasket now if you need your car.
Bright side of that, when you swap the heads over you'll have already had practice, and an idea of whats involved.