Is my maths right please?

My maths has always been cruddy so could someone have a peek at this maths for me to see if I've got it right please?

Starting in May, I'll have £400 left after all the bills have been paid.
I've got just over £4,500 left to pay on BC.
About £1,500 left on SB
About £1,000 left on CO

So, save up that £400 every month and in 10 months I'll have saved up £4,000, right so far?  So, 10 months after May is January yeah?  I'm paying off BC at £75 a month during those 10 months too which adds up to £4,750 yeah?  That means I can pay off BC first that I'm still paying interest on.

I then split the £75 a month between SB and CO so that I'm paying off £75 a month on both of those.

I've got an expensive web hosting bill every April, so have a break just for that one month.

Save up £400 a month for another 4 months and pay off SB.  Move the £75 a month onto CO so that I'm still spending £150 on credit card bills, but it's only going to CO now.

That means that by the end of next year at the very latest I'll have paid off all my credit cards and I'll have £550 free each month which I'll put into my secondary account so that I'm not tempted to spend it!

Is my maths pretty much right?  I know that I'll still be taking off the monthly payments as well as the £400 a month so I'll be able to pay them all off sooner than the maths, I'm just after a rough idea is all