Still having the problem despite all your great help. Here's a step by step of what i am doing which might shed some light on this:

1. Load FS
2. Load 757 at EGKK (also tried various other airports and also tried loading the default cessna first)
3. Open overhead set IRS knobs to 'align'
4. Extinguish all overheard amber lights as described in the FMS tutorial and also the 757 manual
5. IRS to nav once lights are out
6. Yaw dampners on
7. Open CDU
8. Pos init page > Route
9. Load company route i created to save time (also tried with manual routes, tutorial route and direct routes)
10. activate > execute
11. enter perf init page
12. enter perf init info
13. Takeoff page. Flaps 15, 60degrees thrust (tried various other numbers) set CG and confirm vspeeds
14. Set trim on pedastal
15. Computer Select to 'auto' Thrust Red to 'both' and pushed in
16. set flaps to 15
17. FD and A/T on
18. Set IAS to VR speed
19. Check A/T, TO and FD show in greenon display
20. Release brakes
21. throttle up to 1.10 EPR
22. Hit EPR button and it illuminates
23. APR displays on screen

At this point the aircraft is slowly rolling, i don't touch the throttles. The EPR remains at 1.10 and airspeed never rises above 60kts. FMC pages all display 'complete' and as far as i can see i have done everything i have been told, although my routine is probably rather shoddy compared to how it's meant to be done. See anything i've done wrong? fingers crossed and thanks for your continued help!  :)