As someone who spends much of each day looking at values of cars -- especially classic British ones, I have the following advice:
--Ignore Keith Martin, Barrett-Jackson and other "experts" when it comes to values in relation to cars that aren't at auction. Keith Martin charts auctions, but not private sales, so his values tend to be very high in relation to what you can actually buy good classics for. B-J pushes the values of cars that they own and plan to auction. Indeed, the whole "value" industry is extremely self-serving.
That being said, none of the cars on the list are in any danger of increasing in value faster than the overall market for British cars. Why do I say that? The Bugeyes just appreciated from a market value of around $7500 for a very nice one to about $10-12K for a very nice one. This puts it around the same price as other cars which have always been considered "better" British roadsters.
Very nice TR4s can still be purchased for under $10K. Remember these are PURCHASE prices, not ASKING prices. TR4s, for some stupid reason, have not caught on in the market. They missed their opportunity. TR3s shot up in value, then TR-250s, now TR6s. TR4s have appreciated, but more in line with the rest of the market. It would be uncharacteristic of the market to have the 4s rocket up until something makes them seem extremely attractive (such as TR6s selling at $20K.)
Lotus cars have long been stagnated. Basically, because the market for Lotus is so limited, and the cars have such a horrible reputation for quality, the $20K is the ballpark for 7s and Elans. The one exception has been the Elite, which jumped in value about eight years ago, but has since cooled off.
From the perspective of answering the question: "what car can I buy and in five years sell the car for more/break even" the answer is "any of them." The key is to simply buy any car you want and push hard for a price that gives you a little wiggle room. You should be able to buy a good TR4, good Bugeye or good Lotus for what essentially amounts to "under value" if you look hard, do your research and understand how to get a good deal. All of these cars (and almost every car ever made) have a plus-minus on value large enough to find one that is a good deal. Typical stuff -- buy a good car from a motivated seller!!! This means be patient.
Most importantly, buy a car you like. A TR4 is a wonderful all-arounder. The Bugeye is high on style, but lacks in performance and space. The 7 is wild, uncomfortable, dangerous as crossing Interstate 5 on foot while blindfolded. All are fun as heck in their own ways.
For me, I only fit in the TR4 -- at 6'4", I'm too tall for the Sprite and 7. But for you, you'll have to drive them and see which fits.
But the only one I'd even consider making an offer on would be the 7, because the others are too high priced IMHO.