Personally I think Cranfield is a much better choice than Bournemouth, they should be able to get more training route options from there and a lot less training time will be lost because of commercial traffic.
Although it may now be academic, do not agree. Cranfield has no Approach Radar with all IFR movements provided a Procedural Service, consideranly slowing down the movement rate if there are two or more IFR arrivals. Somewhere in the order of 8-10 minutes between each? Integrating training traffic with BOH's minimal amount scheduled plus other IFR movements can be far more efficiently handled by provision of APS rather than APP.
Plus, Cranfield's current operating hours, with ATC manning tailored to them. IMHO frequent extensions of hours to accomodate training would not be practicable due to staff availability cause by ATCOs regulated hours?