It really all depends on what strain of yeast you're using. Ringwood (used by Gritty's, Geary's, Shipyard, etc etc, as you know) is not much like the others. The best way to reduce diacetyl is to; 1) pitch plenty of yeast, for a 5 gal batch at 1.040 I'd be doing at least a liter starter, and if the gravity was any higher I'd go to 1500 or even 2000 mL; 2) aerate really well; 3) diacetyl rest: after primary fermentation is over, keep the temperature up for at least a day, longer with a stronger beer. Also, esp. with a stronger beer, you may need to rouse the yeast (i.e. shake the hell out of the fermenter). Ringwood really likes to flocculate. The idea with all these steps is to have plenty of healthy yeast and to keep it active after fermentation to reduce that diacetyl. I've made Ringwood beers with no detectable diacetyl, so it is possible; it does produce a lot during fermentation, but will clean it up if you let it.
With other British yeasts, as I said, it depends on the characteristics of the individual strain, though there are some general rules. If you want higher maltiness (leaving aside the obvious steps in recipe formulation like using plenty of specialty malts and keeping the hop bill small), choosing a lower-attenuating strain and mashing at higher temperatures are good ways to go. For maximum ester formation, underpitching and underaerating will work, though those have side effects (like diacetyl). The easiest way to increase esters is to pitch the yeast at a high temperature (68-70 F for most British yeasts would do it, and you can let many of them rise to 75 with no ill effects). For the vast majority of British yeasts 62 is a pretty low starting point. The (greatly simplified) reason for all that is that most esters are formed during the growth phase, before fermentation starts and the airlock bubbles, and they're formed much faster at higher temps. So, lengthen the growth phase or raise the temp and you'll get more esters.
As far as temp crashing, I'm a fan, and with most British yeasts they'll flocc REALLY fast if you drop the temp fast. Try to get them as close to 32 as you can, as fast as you can. BUT, with any yeast that produces a noticeable amount of diacetyl (which is most), let it sit a day or so at fermentation temp after the primary is done. You'll end up with a much smoother brew.
Also, I'd be concerned with any 1.040 ale that took 5 days, or any more than 72 hours, to ferment. If it's taking longer than that you're probably underpitching and/or underaerating.
