Thanks for the comments guys, I know people say fit the intercooler etc with the bumper off but i've never had a problem with leaving the bumper on as long as you can raise the car high enough. Plus, getting the bumper to sit straight and look good from the outside is very important imo so fewer bits that could possibly get in the way the better...

...so I think i'll pop the bumper on first, fit the intercooler/rad etc and as said if needs be I can drop them back down when fitting engine!