I'd take the offer with Mazars.. gets you somewhere in the industry and bare with it for 6 months whilst looking for something more suitable. that way you can whack that on your CV as some experience and maybe it'll work in your favor with other firms. I'm in a similar situation with you but I didn't bother applying when everyone else was as I was worried about my grades, now I've got them I wish I applied earlier when there was more apprenticeships going as now its 100x harder trying to even get into an interview phase. Best of luck .. lmk how it goes