Chappo- if you want to buy an adapter for the particular hotshoe of the Sony flashes to trigger them in wireless mode than this might work. I can't tell you wether or not as I do it the other way around:
I trigger all my Sony flashes in wireless mode AND do mix them with non-Sony flashes. This is the cheaper version to the one you suggest. All the non-Sony Flashes have a slave cell attached and the Sony flashes obviously not. You can mix any amount of Sony and non Sony flashes in any combination and trigegr them all when the camera is set to wireless mode. By now we have quite a few threads regarding this issue. I post here once more an answer I have sent to somebody on this forum:
Generally speaking there are three methods of triggering flashes wireless:
(a) with Sony flashes you can use the wireless setting on the camera and flashes. You need to be careful which flashes you use as not all flashes can be triggered i.e. by the HVL-F58AM flash. The onboard flash as far as I can tell can pretty much trigger any Sony flash. So that's the wireless mode in connection with Sony flashes.
(b) wireless with slave cells: Now here it gets interesting: (1) Some flashes i.e. the Metz one can be used in wireless mode (by setting the camera to wireless!) in conjunction with Sony flashes!!! (2) Others i.e the Centon does NOT work when you set the camera to wireless flash mode but you HAVE to set the camera to "normal" flash.
Technically speaking you can buy ANY cheap flash out there. By that I mean seriously any one. I have i.e very cheap Centon ones (about 10pounds max each)/ Metz; and plenty of others. The only important thing is that you need for that either a flash sync cable that goes into a little hole in the flash or you buy yourself an adapter that you can attach to the bottom of the flash on which you then attach you slave cell. Or the newer ones see the link below don't need cables and these little eyes but are attached to the bottom of the flash.
See pictures below.
Pay attention to the Metz one: it does come with the cable but you have to buy the little so called "eye"/ "slave trigger"
My advice would be: go to the next best camera shop buy your self the cheapest flashes you can get WITH either adapter (pic below) and or cable plus "eye" and then go and experiment. The people in the shop will hopefully know what you need for your particular flash to be able to trigger it.
Why Metz? Why Centon? Or indeed any other cheaper brands?
The Metz flashes are usually extremely powerful - that means you need space and have to shoot through plastic bags/ diffusers particularly when shooting close ups. So if you intend to shoot a weding shoot with lot's of people and you want to illuminate whole groups of people than something like the Metz is fanastic. Also for interior architecture shots the Metz is unbeatable. Building quality of the Metz is outstanding. Not sure how often I have dropped mine- nothing ever happened. I sincerely believe you can use them as a hammer.
Something that is much cheaper such as Centon flashes or anything similar is particularly useful when you are shooting close ups or just want highlights on the hair and so on. They have muich weaker output which is sometimes actually important.
Let's assume you would go outside into your garage with a Metz flash and would like to shoot a moddy shot of your car with very controlled illumination? Forget the Metz- you will have to soo diffuse the flash and still your whole garage would look like it is flooded in light. or such occassions you would take 4/5/6... or more cheap flashes (all together cost you under 100 pounds) and would put them strategically around your car. They are much easier to control than one single Metz. So you see horses for courses.
Now to just come back to one point above: some flashes can be used in conjunction with the Sony flashes in wireless mode which is fantastic. The other way around I don't know yet as this would mean to set the camera to "normal" flash and attach some kind of triiger to the Sony flashes. I very much assume one would have to buy an expensive trigger to be able to trigger the Sony flashes outside the wireless mode and frankly theother way around is probably cheaper- dependng on how many flashes you want to buy.
I tend to buy any functioning flash that I come across and get a slave cell (Jessops has them) plus cable.
Here is one unit you can use without buying the cable- mine looks different as it is older!:http://www.jessops.com/online.store/categories/Accessories/Flash/Slave%20Units/products/Jessops/Minicell%20Slave%20Universal-9094/Show.html
Hope this helps?