I've been using Rimmers for (must be) 30 years since I got my first car - a Vitesse - and I think they advertised with the Triumph Sports Six club. They have a great reputation in NZ amongst the Landie fraternity. If you want popular bits (eg brake cylinders) there are places you can get the bits here quickly at decent prices, but anything other than that and the first port of call for lots of people is Rimmers. You can ring - but if you're sure of the parts online ordering is good as you can type out your address. When I got my IRD recon kit from another outfit in the UK, I did it over the phone and they wrote my address down wrong and it ended up bouncing around courier yards before I contacted the supplier then the courier to sort it out - complicated by time zones. You may have to wait a couple of weeks for delivery.
As an idea of how important the like of Rimmers are to us over here. My son needed 2 bushes for his Rover 220 Turbo. Cheapest here we've found is $185. Rimmers were $30 plus $40 shipping.
Mine's an NZ new 1999 car - don't think it has a dimmer for the dash - unless the lights on the heater controls and the backlight on the milometer not working count? Aussie spec may be different. Pre 2000 cars are mainly NZ new, post 2000 are 1/2 2nd hand imports from Japan.