I am in exactly the same boat, but at the job application stage. As mentioned, you need experience on your CV so make the most of your time as an administrator and of your 'transferable skills'. Get certification to be seen but you need experience to be picked up for more than a helpdesk job at £12-15K. My background is very similar to yours and I am getting nibbles in the £25-30K range.
MCSE is the obvious choice for certification but it is really only a starting point. Many employers are asking for UNIX/Novell/Linux as well. Also backup and firewall skills are listed in the 'essential' part of the ad.
I can recommend an excellent training school for MCSE/Cisco and Linux, just email me if you want details or any other training advice.