You seem to making a simple process VERY difficult !!!
driver170 wrote: You wrote this
I am doing a westbound flight into EGLL. I want to be vectored to finals from the last waypoint in the STAR LAM3A. When i create my flightplan prior to compiling in PFE I include all the waypoints of the STAR including the last one LAM. I then compile, and in PFE I then make sure the altitudes at the STAR waypoints are adjusted to reflect the STAR altitudes. I DO NOT tick the box on SIDS/STARS page to enable STARS (cleared to finals). I DO NOT select a start of STAR in the waypoints page.
At the bottom you mention I DO NOT select a start of STAR? I've been selecting a start of star if am flying a STAR?
The way you are working this how on earth do you expect PFE to know that you're flying a STAR? If PFE doesn't know you are then ATC will be giving you various instructions.
The SIMPLEST method to achieve what I believe you are aiming for is to do this....
Create your flight plan but DO NOT include your STAR as there's really no need. You will have to ensure that the last waypoint in your FP is BEFORE your intended STAR. Tick the box in the SID/STARS option and when you reach the final waypoint in your FP ATC will clear you for the STAR, at which point you can fly wherever you want, even if it's not a published STAR, PFE doesn't care and ATC will leave you alone until you are established.