I wouldnt suggest buying a tubular one of ebay, especially if you running more than std 1bar boost as they prone to crack.
My car came with a tubular one from ebay on it, its cracked in several places and has then subsequently been removed and rewelded. It's shocking.
I bought a polished and ported standard manifold either off a member here or across the road I cant remember, that needs to go on.
Unless you running 450 bhp plus the standard exhaust manifold is still decent, especially if its been polished and ported for better flow.
Alternative is a decent tubu;lar manifold from one of the top supplies with a gaurantee (such as JMF, HKS etc) but you looking at 800 quid min if I recall