It will definitely sound different. Whether you consider it money well spent is hard to say. The snag is your current TT is very good for the money (I take it is quite a recent model, the III)
Can you hear the Rega, with the Elys cartridge included at the £625 rrp, in comparison to yours? If not, I'd hesitate to give it a wholehearted thumbs up. You could ask Henley, the Project importers, if yours could successfully take an Ortofon Bronze - if so, that might be a better bet, with money to spare too.
I'm presuming you have a decent LP collection because if not you might feel that the same sum invested in streaming - say, a used Linn Sneaky DS - would give a better return.