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?
IMO, no. See
https://bitcointalk.org/index.php?topic=204322.0. With difficulty now at 15.6 million, I think it's a very bad time to buy GPUs strictly for mining. You may be able to mine some BTC and then sell them to make a tiny profit, but I don't think it's worth the risk.
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?
I discussed that in the above linked thread--current GPUs will hash scrypt altcoins while ASICs will not. However, my theory is that GPUs will shift to scrypt coins (mainly LTC), keeping it roughly in line with BTC, until ALL GPUs have shifted over to LTC. There may be a period at that point where LTC mining is somewhat profitable, but FPGA development is already underway for scrypt, and that will doom GPU mining in the same way.
3) Are there any realistic ASIC options at this point, all the sellers seem rather dodgy to me?
I don't really think so. They are either too expensive (e.g. ASICMINER), unavailable, or delivery date too uncertain.
4) What other angles could I look at other than actually buying Bitcoin of course?
Well, you could always look at stocks on btct.co, but the options are pretty limited.
Feel free to add any other pearls of wisdom that spring to mind...
Thanks for your time.
The numbers have gotten even worse after the 28% jump in difficulty. A 7970 put to work today will likely make less than 1 BTC over its useful life--which is probably only until mid-October before it costs more to run than it earns when difficulty hits about 60 million (this is for 650 MH@250W). Currently, you will start at only about $2 per day, and that likely drops to $1 by the end of July.
Don't start a GPU farm!