While I have not been looking at ASX trades (as it's irrelevant...

While I have not been looking at ASX trades (as it's irrelevant really in comparison with volume on AIM), no, selling 50k-100k then buying a small amount at a higher price is not market manipulation.

I can't see why anyone would do it (how do you know it's the same person anyway?), but it's not market manipulation. I could buy some shares now (on AIM) and sell them right away for a loss, then rebuy them and sell them again for a loss- it wouldn't be manipulation, it would be just me being an idiot.

And remember- these theories only come up when the price is going down. If you believe the idiots on RUM/Worldstocks they'll tell you the price has been manipulated since last April. Except on the rallies, of course, they were caused by genuine buyers. Then the nasty MM's/brokers/hedge fund traders/gnomes in the garden all conspired to drag the share back down, apparently.

I do wonder, if all this 'manipulation' is going on, why has no one reported it to the FSA? It's easy to do, and if you genuinely feel that manipulation is costing you huge chunks of profit, the FSA would like to hear about it.

I'd suggest you'll need better evidence than 'there was a large sell followed by a small buy right after it' to successfully prove your case though.