It's also second stop on the free 423 bus from T5...
423 Bus timetable - Transport for London
...and in all honesty it's not too far to walk from T5, probably about 15 minutes or so but it's not the most scenic route, mostly roadside stuff, so probably best avoided. That said if
do walk and get thirsty there are a couple of pubs on the way as you pass through Longford village before you get to the Thistle..
.