porting & polishing in the midlands?

Not worth it for your spec build, money & effort better spent elsewhere or saved.
You would be best getting exhaust manifold ported & investing in a 2.75 or 3" turbo elbow as serious gains here & only set you back around £250, you could match/taper the head exhaust ports & gasket to manifold too, can do that yourself with palm grinder . Could even do the exhaust manifold yourself if fancy it .

Sounds like sound advice as always MrB,

^ just concentrate on the known weak point & things that troublesome do with engine/box back in.
Exhaust manifold & especially elbow make good gains for little outlay, having a crack at the exhaust manifold could be bit of fun too . I would suggest spending  funds also on decent clutch such as something from Competition Clutch such as CC stage3 segmented 8pad sprung or stage 4 6puk sprung if think you will do fair bit of track or play on drag strip, add a reinforced clutch fork if not got one already & new release bearing. Doing that keeps it strong & trouble free & very versatile for road or track & also handle more power easily should you want it .
drifting a bit from topic so sorry about that :-)

Would a tubular exhaust manifold have the same effect as a polished stock manifold?
I saw this on shitebay;
http://www.ebay.co.uk/itm/Nissan-Pulsar-Sunny-GTIR-GTI-R-AUTOBAHN-88-TUBULAR-MANIFOLD-SR20DET-/321966925030?hash=item4af6b964e6:g:gecAAOSw7FRWYfdu

Cosmic73 wrote:Would a tubular exhaust manifold have the same effect as a polished stock manifold?
I saw this on shitebay;
http://www.ebay.co.uk/itm/Nissan-Pulsar-Sunny-GTIR-GTI-R-AUTOBAHN-88-TUBULAR-MANIFOLD-SR20DET-/321966925030?hash=item4af6b964e6:g:gecAAOSw7FRWYfdu

Everybody here will tell you that they're more trouble than they're worth. They flow and look lovely but welds crack after a while...