Oil light flashing after 3000 rpm

[mk2man1]

Hi all i have just got another mk2 1.8 k jet today.Just had a new headgasket and a bit of head work done.Starts and runs fine no smoke rattles anything.As soon as it goes past 300rpm oil light starts flashing and it starts buzzing.
Could it be pressure switch problems or try another head gasket.It has an almost complete service history never been modified in anyway shape or form and its a one lady owner any ideas.
 Thanks guys

[danny_p]

did you disconect the leads to the switches ?   puttem them on the wrong way round upsets the light

[mk2man1]

Thanks i will give it a go i never did the work to the car i can also check on my other gti what way round they should be.That would be a result if it was.
Thanks