Apple Watch Ultra Chargers

Just ordered Apple Watch Ultra. Was wanting to use with Apple MagSafe Duo Charger that I already own but Watch Ultra is not listed. The Watch Ultra is also not listed as compatible with the USB C 20 watt charger that I own either. In fact it looks like the own charger listing the Watch Ultra as compatible is the 35W Dual USB-C Port Power Adapter so having just paid £849 do I now have to spend another £69 to be able to charge it?