The TD320/321 is basically an updated TD160, with a leaf spring suspension a la Bang & Olufsen.
Thorens have recently released the new TD350 and
TD160 HD which cost a pretty penny and the main differences are an acrylic platter, which I believe you can get separately if you want, superior damping and a Rega derived tonearm. I think the motor may also have some kind of electronic speed control like the TD125.
Is yours the version with the Thorens TP16 tonearm? If so I'd probably start by upgrading to an
Origin Live modded Rega tonearm. Now the UKP has dropped against the Euro it's a good time to buy!
Also while you are there you could also consider their DC motor upgrade and external PSU box which is pretty reasonably priced and should be another easy upgrade.
Acrylic platters are a matter of taste I feel and will change the character of your deck quite a bit, not necessarily for the better. Personally I would get a better platter mat than the stock one.
SRM Design make a nice silicon mat which does a great job of damping the platter on my Thorens TD125 allowing a lot more detail to come through.
If you like the sound of your Thorens I think you might find it better to upgrade than start again with a new deck.
If you want to listen to some new decks other than those by Thorens I'd start with the traditional suspended subchassis decks made today which offer a similar sound but offer further scope for refinement.
Obvious contenders are the Linn Sondek LP12 which costs around 1000UKP without arm or motor and the
Roksan Xerxes , about 2000UKP + motor.
You could put together a Linn with Origin Live arm and motor quite cheaply as above or else there are plenty of motor options from the likes of
The Funk Firm and
Stamford Audio
There are dozens of other new turntables around now but I'd listen before you buy as they mostly sound quite different to all of the above.
The Michell's are also suspended subchassis and very nice but do sound either colder and more modern or not quite so coloured depending on your viewpoint. VPI's aren't quite such a bargain in Europe but you could definitley check out the Scout on your budget.