You can see the UK & Irish WW1 and WWII Wartime Records Collection here. Included are not just the obvious record sets related to military service, but also some church and civil bmd records, school records, Poor Law records, criminal registers and Police Gazette, orphanage registers and newspaper announcements.
To view the records you need to have a registered account with Ancestry.co.uk. If you don't already have one, provide your name and email address when prompted. You'll then be sent a username and password to access the records. It's an efficient, quick and free process.
After the free access period ends, you will only be able to view the records in the featured collections using an Ancestry.co.uk paid membership.