To echo the above: Do a general Psychology degree, unless you really have a burning desire to do an undergrad in forensic. Even if you do the forensic BSc, it'll have most of the same modules as regular Psych in order for it to be accredited by the BPS. Often the difference is pretty minor.
A MSc in Forensic grants you stage 1 of chartership as a Forensic Psychologist. For around £5,000 fee's, it is the easiest stage. Stage 2 is very difficult due to the rarity of positions that enable you to get supervised practice; let alone ones that are paid. Plus, Forensic Psychology isn't a highly sought after area, a lot of Psychologists who work with forensic populations are in fact Clinical Psychologists.
I did an MSc in Forensic Psych and I realised that qualifying isn't really worth it and am pursuing the Clinical route. Having said that, a Master's is useful for getting jobs and on the Clinical doctorate - so it may as well have been that one.