would you use vo2 max intervals increase your functional threshold power using a power meter? As described in this blog post below:
http://www.training4cyclists.com/threshold-power/
Example: 3 x (3+3min) at VO2max / recovery. If you use a heart rate monitor, your heart rate should be above 95% of maximum at the end of these intervals. If you use a power meter, your target power could be in the area of 120% of your functional threshold power or even better based on your 5min maximum power. - See more at: http://www.training4cyclists.com/threshold-power/#sthash.DbD9Dyf9.dpuf

Or would you use the intervals methods described in the blog below:
▼ 10 minute controlled warm up with bursts up to FTP 
▼ 20 minutes @ 85% FTP 
▼ 4 minutes recovery @ 150 watts maximum 
▼ 20 minutes @ 85% FTP 
▼ 6 minutes cool down spinning at 100 rpm
http://www.flammerouge.je/factsheets/functhresh.htm

Or have I missed the point of either recommendation in the blog posts above and are these type of intervals dependant on the time of year?
Those should both be staple type workouts in your folder. There are basically two types of workouts that you should be doing to increase your speed, and both of them are described fairly well in your examples.

The first is a threshold workout - This is a pace that is at or near your race pace, with relatively short recovery. This is the second workout you describe, with the 80-85% FTP. (Remember that an FTP measurement is generally described as the maximum effort you can sustain for one hour). In this you are doing near a race pace, with short recovery compared to the length of the sustained effort. This type of effort is designed to increase the amount of time you can hold a high effort level.

The second is an interval workout, which is what your first workout describes. This is short periods of very intense effort, with enough recovery to ensure that you can complete the next interval at the desired level. If you note, the recovery period (3 minutes) for this one is nearly as long as the recovery for the threshold workout (4 mins) for a much shorter effort. This workout is designed to increase your top end speed.

Taken together over time, these workouts will increase your top speed, and increase the amount of time you can spend near that speed.

They are also somewhat dependent on the time of year. During the "off season" if you will, you should be concentrating on long distance riding, not much intensity, to get a good base for the next year. A couple of months out you should start adding in some of these workouts, and increase the frequency in which you do them through the first few months of the season, then change over to fine tuning and maintenance type workouts. If you are unsure of how to do that, a coach can be a huge help.

As far as measuring FTP, I'm not a big fan of the 5 minute tests. I prefer either an hour time trial if you can manage that, or the 2x20 method, preferably on the road.