Quick update -
Managed to get the tyres on! Thanks for all the tips. Looks like the fact I had them stored in the garage over winter didn't help.
1. Fit tyre with tube to another wheel and pump up as hard as possible without it blowing. Leave overnight.
2. Remove factory fitted blue rim tape on wheels - note this doesn't need to be cut (as mentioned on other forums)
3. Fit the black tubeless plastic rim thingy
4. Mix washing up liquid and water 1:1 and apply to the rim and black plastic tubeless thingy
5. Remove tyre from the rim you used overnight...Fit the first bead - start opposite the valve and work round
6. Fit the second bead - again starting opposite the valve
7. Now add sealant - either via valve or lift the bead a touch with a tyre lever and fill
8. Start pumping and wait for the beads to pop
9. Spin the tyre so that the sealant works round the tyre
10. Go for a ride
Sounds complicated but if you follow the steps it's really no harder than fitting a tube.