Hi, I've done quite a lot of research into this...
There are different types of psychologist, clinical, counselling etc have a look on the BPS website for more info.
If you wanted to become a Chartered Counselling Psychologist you'd need your degree at 2:1 or above. You'd then need to go and do a PsychD for 3 years full time where you'd go on placements and train, plus do a thesis and attend lectures at a university. Its pricey though - about £6k in fees a year. I think there are places that do a part time version that can be done over 5 years but I hear they are v demanding and give little time to work at the same time.
To become an accredited BACP counsellor you will need to do a 2 year part time certificate course (usually only 2 - 3 hours a week), I did mine at Birkbeck who are fantastic. You don't need a psych degree but its certainly a great asset to have for counselling.
Then you need to go on and do a post grad dip/Msc in Counselling which is usually 2/3 years part time (1 day a week in uni then a day or so a week at a placement). Fees are around £3k a year. This route will allow you to work and study at the same time though which helps manage financially. You'll again need to have some volunteer experience of counselling (childline, Samaritans etc) ususally 6 months min.
Again have a look at BACP website for more info. All counselling courses have different approaches (humanistic, psychodynamic, CBT, existential, psychosynthesis etc) so its important to read up on them before deciding which route to take as its a very individual thing.
Both routes lead you to quite different careers, I think the psychologist route will mean you work primarily in the NHS. Or you can set up your own practice. Long term you can move up the ranks and end up on a v high salary. Plus there is opportunity to specialise with certain groups or disorders.
The counselling route is much more competitive and all the counsellors I know have to supplement their income doing another job or work for free. There are lots of qualified counsellors around so its very difficult to make it a paid, full time career.
Erm.. I think I've run out of steam now! Let me know if you have any other specific questions I haven't covered.