First Great Western recently rebranded as Great Western Railway (GWR), so three trains currently have the revised GWR livery. As yet I haven't photoed these, so watch this space ;)

HSTs are also known as the InterCity125, but that particular name has slipped into history. These are being phased out when the Great Western Main Line is fully electrified, these British engineering icons are to be replaced with Hitachi based Class 800 Hybrid (having a Diesel engine and a pantograph) Multiple Units, based on the mini-Shinkansen trains of Japan. Virgin Trains East Coast unveiled the first 9 coach set at Kings Cross and gave it the name 'Azuma' (Japanese for East) whereas GWR unveiled the shorter 5 coach set and named each one uniquely. The HSTs will still be used on services from London Paddington to the Exeter area however they may be replaced completely by the Class 800 in the future. When first introduced the HSTs had a Paxman Valenta engine installed, the longest Valenta powered HST has been in service was with Grand Central, when the type was finally replaced by MTU power units altogether on the GWML and ECML by 2010. Valentas were well known for their characteristic jet plane like noise as they revved up and began moving. The closest type of engine that simulates this is the Paxman VP185, the engine used in HSTs on the Midland Mainline.
Other operators of this type include:
Virgin Trains East Coast
CrossCountry
East Midlands Trains
Grand Central Trains (shortened formation)
Network Rail (New Measurement Train)