As an owner of a 30 year old "3" I have done a few things to mine (owned from new).
If your unit has the motor suspended by a belt then you may have to change this as well as the platter belt as they stretch and allow the motor to droop (easy way to tell is to have quick look under the mat as the suspended type have two screws either side of the motor pulley).
My subplatter had warped slightly over the years (try the pencil test) so I changed this for a metal one and got the improved stability expected but was staggered by the improvements to dynamics and imaging and with Ruby bearing fitted a lower noise floor too.
With taller cartridges (just about everything except Rega) you may have to fit a spacer and for this you will need a sleeved nut (I also had to open out the hole a tiny amount to get the sleeved but to fit). Time do this was about 15 minutes and not difficult. The good news is with the Tungsten counterweight and not having the braces of the later RP3 even with the 4mm of added height there is still plenty of clearance to the lid. Solid spacers are not expensive (go see your local bike shop for headstock washers) but you can buy variable ones (OL version for me). You can always try without spacers first.
I also had an Elys fitted and it's not a bad cartridge (there are better) but I am surprised your dealer did not advise of Rega's trade in scheme where when you hand in your old cartridge they give you a discount against a new one. This should make the, already cheaper, Elys 2 significantly cheaper than the 2M Blue.
The 2M blue is a nice cartridge but is quite expensive for a nude elliptical tip.
The Elys2 is probably the lowest cost option
AT120Eb is also nude elliptical ~£120 can be a bit bright in some systems.
AT440MLb is nude Microline ~ £170 can tend to brightness dependant upon loading
The earlier generations Ortofons are available from Thakker e.g. Super OM20 €169 and Vinyl Master Red €179 are both nude elliptical too.
You can even pick up a NOS P77 nude Parabolic (line contact) styli and tested bodies here (£155) http://www.theaudiofiles.co.uk/items.html
(I have no affiliation with the company other than a satisfied customer)
Other options (bonded not nude) Nagaoka MP-110 or Shure M97XE
Lots of options but if you are struggling with IGD etc then perhaps the more sophisticated tips of the AT440MLb or P77 may suit you.
(LP) Rega Planar 3/RB300/A&R-P78+FG2 (CD)Rega Planet-2000, (Amp) Musical Fidelity A3.2, (Speakers) Rega RS3