Verdict: Yummy! I omited the mixed spice as I wasn't sure I'd like it. Next time I'd use slightly less black pepper - 2 tsp is really quite a lot but it was still really yummy and I'll definitely be making it again!
Oh, and I didn't bother boiling the chicken first - just sliced up raw chicken and coated it in the bovril mix then rolled it in breadcrumbs.