Flight Plans and Entry to Controlled Airspace

[Desert Strip Basher]

Been hearing a few stories lately of IR training flight plans in the system but London/Scottish control simply advising to contact LARS and binning off out of controlled airspace asap and/or not necessarily accepting entry to controlled airspace on return legs - again to negotiate a route with LARS units. Seems a bit unsporting and I'd far prefer to be safer in controlled airspace as per my flight plan - is there no obligation from NATS to provide a service once a flight plan has been accepted? I can't imagine airspace <FL100 is that busy down low for your typical MEP so not sure what the reasons are. Any advice or general experience appreciated.

[custardpsc]

Try asking again in the ATC section. I asked a similar question about exactly this, specific to the london TMA and got a really helpful set of responses.