Yes Chris- you have a brew boiler full of descaler. Dual boiler machines are difficult to descale.
Best bet is to flush a heap of water through the group. Try perhaps 10 litres in the hope of diluting the descaler sufficiently so that you can use your machine.
Failing that, you can disassemble sufficiently to drain the brew boiler, then refill with fresh water before reassembly.
As always with descaling, you only do it if required ;)