I noticed today while changing plugs that my front cylinder head has developed a leak around where the gasket seats. Its not spewing or anything just an oily deposit (for now).
Would this cause a compression drop on those cylinders?

how much oil do you mean? Is it on the surface around the gasket joint, or is there oil running from the gasket?
Do you have a pic?

No, its only around the gasket surface, externally. Sorry don't have a pic.

Mine looked like someone has smeard a line of oil around the gasket and there is a little line like a dribble, but just on the surface. I just think it is the gasket absorbing some of the oil and passing it out. Has the performance changed?

Can't really say about a performance change, just goosed my plugs over the weekend.
But prior to that, I had a dyno done and was surprised at the low BHP result (50)
That's why I ask will it affect the compression?

What set up do you have? Exhaust, carbs CDI?

I have 120 jets all round, standard induction with a half Ethos system with a Tyga C/F race pipe (no baffle). Its a road bike.

When you say goosed your plugs, do you mean they were knackered, and you changed them?
If they were in the engine whilst on the dyno, that may cause a slight drop in power.
I am sure that someone will correct me if i am wrong, but i dont think you would get any more than 60bhp with standard engine and exhaust. so if the engine is a little tired/done lots of miles and the spark plugs are a little worse for wear than i am guessing that 50bhp is about right. Did the dyno guys put the 120 jets in or did you put them in?
Is this an NC30?

Is the oil leak at the cam cover gasket or head gasket ?

If its the cam cover gasket take the cam cover off, clean the surfaces and apply a smear of gasket sealer all the way round the mating surfaces, job done.

afraid not ,its the head gasket. ita a NC30. I did all the set-up myself before the dyno run, maybe the plugs were on their way out, but the question is, will I be losing compression with the leak?