Before throwing money at the car, make sure all suspension rubbers and ball joints are in good condition. Decent poly bushes all round and the already mentioned “anti-dive-kit†will improve the car's handling very much.
Next get some decent dampers, I'd say Koni (but then I am biased [:p]). There are other good ones around but not that many. If you choose adjustable ones don't set them to hard. Most people try to hide a wallowing ride by setting the dampers to hard. Maybe after that you think differently about new springs.
If not, I have two cars, a DHC with uprated 200 lbs springs all round and adjustable Koni’s set on the soft side of their medium setting. Car is very comfortable and predictable to drive, but can keep up with much faster modern cars on the twisty bits if necessary [:D]
And a FHC Sprint that sits on 326 lbs front springs with the dampers still at their softest setting. And all my fillings are still in place. Rears still not fitted but they are equivalent to 240 lbs, ones fitted in the position I have in mind ...
<center>
<font color="blue"><i>1980 TR7 DHC (my first car, now restored and back on the road)
1981 TR7 FHC Sprint (better known as 't Kreng)</font id="blue">
<b>[url="http://www.tr7beans.blogspot.com/"]<u><b><font size="2"><font color="red">My Weblog</font id="red"></font id="size2"></b></u>[/url]</b></i></center>