Bit of feedback for the Virgin Media Big DATA Tarrif. I picked a SIM up last month and topped up £10. Called 789 to switch the tarrif over to the Big DATA then waited for it to be enabled. 15 days before the end of the month it was activated and I got my 300 texts and unlimited DATA.
Speeds are excellent. Fastest download speed I can get consistently is 600kB/s and this is with 2 bars of signal on a USB dongle stick (as my phone is being repaired). Services like TVCatchup and bittorrent work fine.
I'm not 100% if the package is fully unlimited as the information shown in my account has an allowance of 95GB per month - however this looks like it rolls over so this might just be a quirk of the system not showing the unlimited status properly.
There IS a fair usage but it's extremely fair. If you download more than 10GB of DATA then between 6PM and midnight you are throttled to 3G speeds. Outside of these times you can get your full HSPA+ speeds. Since I got the SIM I've used 25GB of DATA.
I consider this to be a perfect pay as you go SIM for the Orange San Diego as it will function without the device being unlocked. You will need to cut the SIM down as Virgin Media don't provide microSIMs yet. Also if you have a mifi or a tablet then this is also idea for them. The terms & conditions do not explicitly state you cannot use the sim in a dongle (they just say the service isn't meant for them) but I assume if you take the piss they will politely ask you not to.. but they really don't have any way of detecting dongles unless they checked IMEI nunbers against databases. I would strongly suggest you don't use a Virgin Media branded dongle with this SIM though as they are likely to have the IMEI numbers listed.
So want a SIM? Get one of these. £10 a month top up = unlimited DATA, 300texts plus your £10 for use on calls.