An loan with no interest or payments for a whole year and then an ongoing rate of 2.5%...
You’d be crazy not to take advantage of that.
Even if you just took the loan for the interest free period and stuck it in premium bonds for a year then repaid it!
But if you have practically any other loan or finance outstanding, simply pay it off with the bounce back loan, as it will probably not be on terms that as favourable.
And as for needing a business account, well apparently HSBC will open a temporary “feeder” account for you, from which you can transfer it to the bank of your choice. See the comments section on the MSE page.
https://www.moneysavingexpert.com/news/2020/05/small-business-boost-as-bounce-back-loans-launched/Word of warning though, if you can’t trust yourself with a large amount of cash on hand, and will be tempted to spend/squander it, then steer well clear.