@Martyn Baker
If you brewed your Admiral kit to 32 pints (18.5litre) as intended this should give an OG of about 1.047 according to the Brewers Friend calculator, which others seems to bear out looking at one or two of the kit reviews here
https://www.thehomebrewforum.co.uk/threads/woodfordes-admiral-reserve-review.17834/
The claimed ABV of the kit is 5.5% which is achievable given the OG guesstimated above and a likely FG of about 1.010 with an allowance for the priming sugar. So about 1.010 should be your target FG.
The Woodefords kits are made by Muntons, who, in the past, have had a bad reputation for kit yeast, and this may still apply. My suggestion to you is to repitch with another packet of yeast, preferably rehydrated for about 15 minutes in about 100ml of cooled boiled water at about 25*C in a sanitised jug. If you have a Wilko near you, get down there and look for their Ale yeast which has been a saviour to many restarting a Muntons/Woodefords kit.
Best of luck with it.