First off, Ultra-violet sounds a lovely colour! Why alter it????
O.K. then, did you have any, type of permenant 'blonde' on it before, dying it Ul.-Vi.? If so, you will 'still' have peroxide 'in' your hair . . .
If, it is a dark, violet colour, you will need to bleach it a few, times before getting it completely clear of it (this can, take a few weeks)
(remember how I had to stay that 'gingery colour for a spell)
Think hard, about trying to do too much too soon - you will get the dreaded 'doll's hair' effect!
You might be better off going to a hairdressers and get it done professionally - I can recommend 'Tony & Guys' salon in Swansea. They are, a tad expensive, but damn, they are good - I can give you my card which may, give you a discount the phone number is: 01792 465533 & their website is: www.toniandguy.co.uk
Don't do anything stupid - you have a perm as well don't you? Be careful!

- Hhhhmm,something vibrant . . . now, what have I got that vibrates . . . could do the trick
(no Lynnette, if you add a comment here - I haven't got a vibrator)!!!