Hi Andytred
The tides around Swansea are quite strong. With an uptider you can still use fairly small weights and still hold bottom. A good uptider should have a flexible tip (so the boat movement does not pull the grip weight out) but should then be fairly stiff in the middle, and butt section to give good lift of heavy fish. Fortunately there are loads of suitable uptiders and you can get a reasonable one for around £20 - £30 with a top of the range one around £100. Ive used both ranges and apart from the expensive ones tend to be lighter, and are slightly nicer to use I didnt find much difference (they both catch fish). Another advantage of an uptider is that it can be used as a short range beach caster, which can come in handy if your boat trip is called off at the last minute.
Regarding left hand reels you wont have as much choice. The most commonly used uptide reels are the ABU 7000 range. I prefer the level wind version but thats your choice. ABU reels tend to go on forever, I bought my 7000 nearly 25 years ago and its been used and abused ever since. Its needed only 2 new spools and a new handle in all that time. I believe there is a left hand version (I think its called a 7001) which may be worth you considering, its not the cheapest reel but Ive owned loads of cheap reels and they just dont last.
Hope this helps, good luck with the cod.