The UK polling for the European Elections has largely been national, with separate polling only (that I've seen) for the London region. So it's hard to work out what's going on in my "South East" region. Here's my attempt at an analysis.
First, looking at the 2014 results (official PDF) we find that 2,338,050 votes were cast, with the breakdown of votes and seats won:
UKIP - 32% - 4 seats Conservatives - 31% - 3 seats Labour - 15% - 1 seat Greens - 9% - 1 seat LibDems - 8% - 1 seat
And here's the list showing the order of election:
UKIP just took 4 seats (they took the 10th spot), and the LibDems just took 1. Labour just missed out on 2 seats.
Flavible has a prediction: looking at the South East region on the right-hand map on this page, their "tracker" numbers as of May 12 suggest 4 BXP, 2 Conservative, 1 Labour, 1 LibDem, 1 Green and 1 CHUK. But their methodology for CHUK seems dubious. ("The baseline for the ChUK is currently set as the projected values of the average swing from each party. For example, if the support for the ChUK stands at 7%, with 2% from LDem, 3% Lab, 1% Con and 1% Oth, a projection will be made with these numbers to get the predicted support per constituency. This will be used as the baseline.")
BXP seems likely to pick up almost all the 2014 UKIP vote. Looking at national polls, they may be up a bit percentage-wise on that, but that's unlikely to give them five seats here.
The Conservative vote has clearly collapsed, by more than 40% looking at national polling, but they're still going to take one seat easily in the South East, much as it would be nice to get rid of Dan Hannan, and almost certainly a second.
Labour was unlucky not to get two seats in 2014. The national polling suggests their vote could be down a little, but getting a second seat here is possible.
The Greens should hold their one seat. They outpolled the LibDems last time, but the LibDems are on a roll (up 60% or more on 2014 in national polls) and so seem much more likely to take two seats than the Greens. The South East is possibly CHUK's best chance for a seat, but it still seems a difficult task given the national polls.
My unexciting prediction for the South East is BXP 4, Conservatives 2, LibDems 1, Labour 1, Greens 1, with the 10th seat (lost by the Conservatives) going to LibDems, Labour, or CHUK (with the first most likely and the last, least).
Possible variants on this include BXP only taking 3 seats (or just possibly taking 5), the Conservatives managing to hold onto 3 seats (or only holding 1), and UKIP pulling off 1.
Tactical Voting? At least in the South East, Green voters should stay Green (there's not enough margin on the seat they hold to risk tactical voting). Labour Remainers should probably refrain from trying to send a message to the party leadership and stick with Labour — though I'm having trouble finding out much about the stance of their second candidate, Cathy Shutt — or switch to LibDem. Remainers switching from the Conservatives should I think vote LibDem rather than Green or CHUK, and people thinking of voting CHUK should probably go LibDem too. (This is not symmetric. Going the other way would risk neither party getting a seat, whereas backing the larger party here gets 1 for sure and maybe 2.)
Update (20 May): given the polling, I think the chances of Labour picking up a second seat are vanishing. So the best Remain option seems to be the Greens getting one seat and the LibDems getting three seats, with Labour getting one. This requires CHUK voters to go LibDem (or Green or Labour), and defecting Labour and Conservative voters to go LibDem. See the Best for Britain analysis for the South East.
As this vote's sole purpose is as a de facto protest about Brexit, or non Brexit, sure you can just simplify your tactical voting pattern Remainers vote LibDem as that is their main policy and Brexiters Brexit as that is their only policy.
Nobody should vote for the Conservatives, Labour and certainly not CHUK until they follow the most basic principles of the Westminster System and resign and call a general election to allow the people to vote in a new government to fix their mess.