They can definitely be lowered. I parked next to one once, and the difference between it and mine was quite noticeable.
Lowering's a purely cosmetic thing, so only you can decide whether or not it's worth the money to achieve the look. Personally, I like to keep my cars as close to stock appearance as possible, so this kind of thing doesn't really appeal.
If I was inclined to do anything with your car, it'd be to go for some bigger alloys to fill the arches a bit better without adjusting the ride height. 15" just look far too puny on the Lag, and I'd say it takes a minimum of 16" for it to look sensible. You might just snap up a set of standard 16" from someone who's decided to go bigger, or you could bit the bullet and buy new 17" or possibly bigger. If you're buying second-hand, then remember that some Lag 1's had 4 stud wheels, while others had 5. Make sure you get the right ones.
I wouldn't even contemplate lowering any car if you ever plan to tow with it. Even if you don't, killer speed bumps will become more of a problem. From a handling point of view, it may make it better or it may make it worse. You won't find out until you give it a try.
Again, it's up to you as to what looks good, and whether it's worth the cost. Check out the following link (found on Google) and it's showing the same part numbers for the 5 stud Lag 1 and the Lag 2, so wheels off the Lag 2 should fit. 19" appears to be about as far as you can realistically go, though looking at the prices will probably make you want to compromise on something a bit smaller anyway.
If you go for Lag 2 alloys, then most of the 17" ones on offer will be the Silverstones. Beware, as these are notorious for being made out of silly putty and buckling if you drive over a pebble at more than 10mph.
Hi there, GFS, GSF Car Parts, cheap car parts direct to you stock lowering springs for the front of your Lag (35mm drop) at £45.00 each + vat,
however, if you wish to lower the rear it will mean adjusting the torsion bar as there are no springs and this will mean the use of special tools to re- adjust the suspension geometry,