Stu - Several things to comment on here:-
1) I fully agree about Warlord; the moment those rules were released, people who had been enthusiastically awaiting them were complaining about the obvious lack of play-testing and glitches. Ditto Warlord abandoning them once the initial "got-to-have" purchase frenzy was over and folk started noticing the obvious gaps in the system. I believe that the ship range has now been taken over by Skytrex, which is another manufacturer to look at for 1:300 ships of their own that have been out for some time.
2) In terms of rules, have you tried TFL's Coastal Patrol (it's in one of the 2011 Lardy Magazines - Summer, I think, but check)? It's more of a "beer-and-pretzels" game, but none the worse for that; and frankly, if you want serious coastal warfare games, I would go for one of the rule sets by David Manley, who is an absolute guru on the subject.
3) Spanner's link is to a manufacturer that focuses primarily on modern stuff and also the bigger, capital ships - the mind boggles at what sort of space you'd need for that Jap aircraft carrier in 1:300!!! I may be wrong, but I suspect also that a lot of them are not waterline models, from the fact that you can get name-plates for many of the ships, which means some quite extensive surgery..... This might be a more useful link:-
https://www.wargaming3d.com/2019/01/16/ ... ruel-seas/
This lists virtually every type of vessel you will need for coastal warfare, and who to get them from. Most of them will print and post to you (for a price), but many sell STL files. Doug on here has a 3D printer and has certainly been generous to me in the past - he may well be open to negotiation for future assistance!
4) Don't write off 3DP! I've gotten some superb little boats from an eBay seller called <<dobsonhouse>> (I think he's also called "Magpie" commercially) and another called <<3dprintstudio>> - typing either of those into an eBay search, minus the chevrons, but plus "1:300 model ships", will give you their listings.
If you know somebody with a 3D Printer, this collection is useful for slightly less common types:-
https://www.thingiverse.com/hendrikdc/c ... -300-ships
These guys are US-based, but produce a very wide range:-
www.wargaming3d.com/product/fairmile-b-sub-chaser/
5) In terms of vessel size/category, I wouldn't go larger than a Flower Class corvette or a Hunt Class destroyer in 1:300, or you will need to start borrowing dining tables (and a warehouse to set them up in)! Both vessels, when equipped with the more powerful surface radars available towards the end of the war, were used to control small groups of MTBs/MGBs. Once you get past that stage, drop down to 1:600, where you will find manufacturers easier to source - Skytrex in the UK and PT Dockyard in the US are two that I have used extensively.
6) If you PM me your email address, I can send you two articles written in support of the Society of Twentieth Century Wargamers forum, involving coastal patrol skirmishes in the Med. Unfortunately, neither seems to still be available via that forum. Frankly, these are much more interesting - and less one-sided - than the normality of USN v IJN actions, although the second article does involve a lot of Elco's and other US craft, so you can still get to use what you already have.
I hope that was helpful - if you want any other links, let me know and I'll see what I can dig out (my own 1:300 collection is more or less complete now, so I haven't consulted the list for a while!).
BvW