I have received an email from 'Model Rail' regarding the above titled publication

"Britain's Preserved Locomotives: The Complete Guide is the only fully-illustrated publication listing every preserved main line British steam locomotive, including those surviving overseas. Written by the Steam Railway team, it is packed with useful facts and information about our preserved locomotive fleet, including their current locations and statuses. Each entry in this 178-page bookazine is illustrated, with an accompanying fact file containing the essential information about each individual engine, its history, significance and preservation career – as well as technical data.".

It apparently has details of 537 locomotives.

Apologies if this has been mentioned previously, but a a quick search showed nowt 

https://magsdirect.co.uk/magazine/britains-preserved-locomotives-the-complete-guide-2018/

https://www.greatmagazines.co.uk/steam-railway-specials

Fairly sure I've seen this in WHS, but just ordered from Great Magazines via Quidco for £2.50 cashback.