Maybe have Shared Slaughter as the 5th round game rather than 1st. In my experience keeping the simpler objective scenarios till last helps with the incremental brain fade that you get at tournaments, especially for guys like me who've discovered their new favourite game has a steeper learning curve than Hordes/Warmachine :Confused_Puppet2:
As for moving the event to earlier in the year. Other than avoiding the obvious clashes with other wargaming events, if you're looking at February or March check it doesn't clash with any Six Nations fixtures, Cardiff will be packed and you'll probably lose a few potential local attendees.
Cheers
Phil