As per title any reccomendations on what to use?

The standard exhaust gasket has always done fine for me. Unless there's something that would stop you using one?

As per my other post here - http://www.locostbuilders.co.uk/viewthread.php?tid=189530

I am thinking of taking the manifold off and refitting to check that it is sealing. Was hoping to give it a smear of somethign at the same time just to be sure it is sealing.

Shouldn't really need anything on the gasket to get it to seal, what would be a better idea is to check that the exhaust face is nice and flat. Other than that it should seal just fine.

However I do see some people use that copper gasket spray in some cases for various gaskets

You could try a thin smear of exhaust paste. Don't use too much as you don't want to risk partially blocking the ports. Not sure if they are sensor safe though.

http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_164909_langId_-1_categoryId_255217

http://www.ebay.co.uk/itm/Granville-Exhaust-Assembly-Paste-140g-Car-Maintenance-Sealant-FAST-DESPATCH-/261278145127#ht_1289wt_1031