Could I have some advice please?

This will be quite tricky. The part of your hair that lightens fastest is the first cm or so due to the heat from your head. The previously processed lengths are also likely to process quicker (providing all the old dye is out) So you will probably need to start applying on the re-growth but avoiding the first cm, then do the lengths and do the roots last.
To check for timing you are going to have to do some strand tests, that is the only way to be certain how well/quickly your hair will lift.

Thank you for your help 🙂 xx

Tbh the colour I wanted to go is a box dye which contains ammonia and peroxide (I don't know the strength) but after doing some research I think it will deposit colour which I'm hoping will even it out.

After reading a lot of posts on here which are really helpful (I've recommended this forum to few people now) I know it's not an easy or quick process to get to blonde especially if uve got a dye (I've really gone off reds and warmer browns because of the info about cuticle staining)

Anyway this is the colour I'm hoping for and going by the colour guide on the back I thought it might be a bit more attainable??? Sorry about the link it won't let me add the actual picture it says the file is too large!

https://www.google.co.uk/url?sa=i&rct=j&q=natural+frosted+beige+blonde&source=images&cd=&ved=0CAcQjRw&url=http%3A%2F%2Fchibichic.co.uk%2F2014%2F10%2Floreal-blonde-hair-dye-review%2F&ei=8teWVMn9KM-Q7AafsYD4Dg&bvm=bv.82001339,d.ZGU&psig=AFQjCNFYUZczajl36ECXGZF0N6kSuDzAMg&ust=1419258224175510

A blonde box dye won't even it out. The natural roots will still be darker and more orange than the lengths. If it lifts your hair by two levels there will still be a difference between the two colours, as they are a shade apart to begin with if you see what I mean.

I get it, thank you I can live with that. I was planning on seeing what it turned out like, toning it then leaving it 8 weeks before doing it again. I baby my hair normally (wash it and allow to dry naturally with no heat styling I probably use my hairdryer and straighteners once a month) and from other posts I think 8 weeks is a good rest time.

When I do it the second time Ide do the darker bit and the re growth. I've not had much practice with going lighter so I don't mind if it takes a while to get there Ide rather keep the condition and sacrifice the colour until I get it right, having fried my hair once before (powder bleached it 6 times in 3 months it went from dyed dark reddish brown to actual WHITE!!!) my hair was cut off from nearly the middle of my back to my jaw line. I was really angry with myself that I hadn't been more patient and just put up with it

If you are concerned about damage, you are better off following Wicked Pixie's advice. Box dyes are not less damaging than bleach, and using them twice will likely leave your hair in worse shape with less lift in color levels than using bleach.