The Hog's Head is a large venue, with many features.  As you enter there is seating to your right and along to the left as you head towards the bar. Although the bar is a fair size I can imagine how it must get busy.  There is more seating to the back for the toilets can also be found. To the left though the arch way is a pool table, another bar and the Venus night club (only on Thursday and Fridays, otherwise just part of the seating area). If you visit early in the week this is an excellent venue, the food is reasonably priced and pretty tasty (I had ham & eggs on my last visit) the London Pride was of excellent quality.  Later in the week, both lunchtimes and evenings gets very busy, be prepared for a busy time.

My advice is to get to the Hogshead early and stake your place, this could be one of the best nights you've had in the City.