If you do the IR first you need all the help you can get.
Hour build while studying. If your brave enough do some of it at night helps later on with the 100hours for ATPL.
Also try and get some twin time in before starting CPL or IR it saves alot of stress later on and it all goes towards your 150hrs.
I didn't make as much use of the hour building as I should of, so its important not to just punch holes in the sky. Have a goal, plan it properly then fly it as exactly as possible. If you did your PPL in the states go for a few Nav lessons with a UK school. MY nav was very slack and looking back on it had more to do with my hillwalking skills than proper Nav technique.
MJ