I have tried to do a lot of research and used calculators etc, however there is a lot of guesswork and I would appreciate more informed opinions.

With ASICs on the horizon - If I were to invest in GPUs:

1) Am I likely to get at least my money back?

Right now, yes.  It will depend on how many months you will mine 24/7, but you can earn your money back.  If I had to guess long-term the answer will still be yes because there are some promising Alt coins out there that are gaining momentum.  

2) Are there realistic options in Alt currencies that the GPU could be useful for vs ASIC - can ASIC at this point or in the near future be used in Alt?

There are several Alt currencies that you can look at for GPU mining.  I like WDC, DGC, BitBar, and Litecoin.  Check out http://www.coinchoose.com/ for profitability compared to Bitcoin or Litecoin.

And, yes/no, ASIC machines will not work well on scrypt based Alt coins due to the memory demands of the scrypt algorithm.  There's only a few Alt coins that an ASIC machine will work on right now, just check which alg the coin uses.  ASICs like the SHA-256 alg.

3) Are there any realistic ASIC options at this point, all the sellers seem rather dodgy to me?

You should define "realistic."  If you mean more affordable (Around the $1000 mark) then the answer is yes, but you may have to wait (pre-order), or buy from eBay.

4) What other angles could I look at other than actually buying Bitcoin of course?

One option that I haven't seen on here yet is trading BTC on an exchange.  Be careful though because loosing money is almost easier than earning it.

Feel free to add any other pearls of wisdom that spring to mind...

Thanks for your time.