Ok, so y’all are getting some objectively terrible advice here. :)
Off the top: yeah, I do think coastal are hard trees to grind and the British trees have problems. And yes, the AB bonus of 30% on the next vehicle in the tree can help more in some trees than the RB bonus of 10%. But… not for British coastal though.
If we make a table of the ships you need to grind that have tree bonuses, and compare them with the average Statshark RP/spawn in that vehicle for June, both raw and with the 10-30% tree bonuses, and figure out the number of spawns you’d need to grind with average play to get to the next vehicle, you get this:
Spoiler
TLDR: Nearly every British coastal boat is getting ground out faster in RB currently. And if you chase the 10% bonuses in RB instead, you’ll finish the whole tree in RB in around 5,500 spawns, as opposed to 5,800 doing it in AB. (Yes that IS a lot of spawns. I would blame small split trees because of the bluewater/coastal split more than decompression though. It’s actually less than that because service records don’t count the end-game RP rewards, including rewards for winning, though, only RP accrued in game.) If you followed the advice you got in this thread, assuming 3 spawns a game, you’d be wasting 100 games worth of your life.
So what’s the real statistically provable advice for British coastal? Well, you can get a good idea by putting this same chart into a scatterplot, with research cost on the x and number of spawns to get the next boat on the y, with a linear line to separate the good boats (low) and the bad boats (high)… expressing here as a log graph to give more room for the labels at the low end:
Spoiler
So if possible, you want to stay below the line here, jumping from point to point below the line to be your main boat as you go up. What you can see if you know the boats, is a lot of the Fairmiles, objectively terrible, are on the wrong side of the line. No surprise. But there are some really good performers (again, lower relative to the line is better: Brantford, MTB-460, Dark Aggressor/Fairmile C (312), Fremantle, and then the easy peasy days once you get to British rank V. You can basically see the big gap between Dark Aggressor and Fremantle with no options below the line. That, my friend, is where you are (I used RB data here but I ran AB and it’s basically the same).
The stats show that, to succeed in Britain, you need to dwell around 2.3 a bit, where it has both very strong and very weak boats, skip 2.7 altogether if you can, and once you get to the 3.0 lineup you’ll have no worries. The two British 2.7 coastals are very weak and can be skipped: but the 2.3 lineup of Brantford/MTB-460 carries quite well, and either the Fairmile C (312) or Dark Aggressor makes for a solid boat #3. All the Fairmile D’s are terrible, so is the H, and so is the Arrow; I’d ignore them. Once you get to 3.0 though, Fremantle, backed up by Grey Fox/Fairmile C (332) is a perfectly acceptable lineup to carry you up into the really good stuff Britain gets at the end. Best of luck :)
EDIT: Two other things that make 2.3 the BR to dwell on until you have 3.0 researched: because of the max-4 top spawn rule, you’re somewhat less likely to run into 3.3 destroyers than you do at 2.7 (and you see no 3.7 destroyers). And the British air at 2.3 is quite competitive, with a combination of a good squadron vehicle, some cheap premiums, and the Hurricane IIB, which makes a difference, whereas they don’t get anything better non-premium at 2.7.
