Zoe44,
First, Your choice of program after BSc don't show progression to my own knowledge, so as stated by others, try go for masters then reapply.
Secondly, your sponsor account is in another country and not your country of application. this may tell the VO you wont return after studies. So my advice here is, take ur time apply for masters for may or Sept 2021 , if possible let your sponsor send the money to your account and wait till after 4 months with LOE to back it up when applying.
Lastly, don't you have properties in your name that will stand as home ties, which with explanation in SOP will help convince them you will come back. I believe attaching leave letter from a company works if its a well known company, but still that not enough as you don't have pay slips.
My humble opinion though.
All the best.