1) Should I go MiniDV or SD card or Hard Disk
Depends on your method of working and personal choice. You've probably seen other threads debating this. Tape tends to give better quality for the money; this is still true in the £300 range; £400 is tricker, as there aren't really any DV models in that range.
As well as the quality for the money, tape gives you an instant archive (save the tape). HDD and SD you need to consider how you will backup material.
Also consider how you will edit. I you want to quickly access a specific clip, and maybe avoid editing on a PC altogether, HDD/SD is much easier. If you are going to shoot several hours of video on a family holiday, and carefully edit this down to a 30 minute movie, then the time it will take to capture the tapes isn't such a big deal, and can be made up by being easier to edit.
2) I have seen the Samsung VP-HMX10 but for love nor money can i find any reviews - Amazon have this for £399 which seems good value for money but is it any good?
I thought you weren't bothered by high def?

I've not seen any video from this model to judge. I'd expect it to be similar to the Sanyo Xacti (review here)
http://www.camcorderinfo.com/content...der-Review.htm 3) What is the best software to edit movies stored in MPEG4 as this seems to be a sticking point with the SD card and Hard disk machines - i am used to the simplicity of Windows Movie Maker but i realise you cant edit the MP4 files (H.264) using it?
There are several flavours of MPEG4/H.264, e.g. AVCHD. For AVCHD either Ulead Video Studio, or Sony Vegas Movie Studio Platinum. I'm not sure if these edit the Samsung.
4) Do all cameras have the equivalent of the Sony Steadishot technology as this worked really well on the current sony i have
Yes, they all have some sort of image stabilisation. Better ones have optical image stabilisation.
5) Can you recommend any machines that would fit my requirements and point to some reviews if necessary.
For miniDV, Panasonic GS230, or the GS320/330. The latter is trickly as 320s seem to be in short supply, and I don't think the new 330 is generallly available yet.
For HDD, the Panasonic H250, or Sony SR190.
Note everyone has new models coming out very soon.