Personally, I'd say no - the engine alone is gonna take a bunch more money to get going. If it were just an outboard, you could just swap a non working one out, but with an inboard, you're kinda stuck with working on it. The rudder looks a bit odd, but I'm no Top Hat expert, so I'll leave that to the others to comment on.
That said, it'd probably be good for you to look at with MB as he's so nicely offered, so that that way, when you see something you really like, you might have a bit more of an idea of what you're looking at!
Had a quick look at others in the same price range - I reckon these would also be worth looking at, all listed lower than the Top Hat you linked;
Contessa 26
www.boatsales.com.au/boats/details/1971-contessa-26/SSE-AD-4472388/?Cr=2 Endeavour 26
www.boatsales.com.au/boats/details/1980-endeavour-26/SSE-AD-6443066/?Cr=9J24
www.boatsales.com.au/boats/details/1984-j-boats-j-24/SSE-AD-6386859/?Cr=11 (a bit racier)
Endeavour 24
www.boatsales.com.au/boats/details/1973-endeavour-24-mk-ii/OAG-AD-16394769/?Cr=22Cole 19
www.boatsales.com.au/boats/details/1982-cole-19/SSE-AD-6664676/?Cr=19 (a bit smaller, but looks in pretty good nick)
Jonno's an interesting guy. I've picked up some amazing bargains of bits and pieces from him, but you kinda have to know what you're buying to be sure of it. Most of his stuff is picked up as salvage, which he then pulls apart for the best bits and pieces to move on. If it's your first boat and you're more interested in sailing than in refit, possibly not the best choice. However, he's really handy to know if you're looking for help on old, discontinued parts, a dinghy to get to the mooring (he has a heap sitting round at Woodford Bay at various price points) or need help organising a mooring.