Is an upgrade to fibre a worthwhile move?

[#1]

I've had fibre at two previous properties, and would at the current one but for some Openreach database problems preventing the install.
From my perspective, 10Mbps ADSL is fine for one or two people working (so long as you find the upstream acceptable), or for one person streaming.
With a family trying to do things - perhaps multi-screening too - a little more would be fine, perhaps 15Mbps.
I wouldn't be too happy at 5Mbps.
The wife has VOIP and conferencing requirements, so we need upstream to be a little better than plain ADSL.
We had (and should get again, soon) 80/20 speeds which handle anything we throw at it. 40/10 or 40/20 would probably be enough, easily.
Edit: What Terranova says about crosstalk is true. Don't expect the speed you get on first connection to be maintained forever - it is likely to start out higher than the estimate (especially on a newly-installed cabinet), and drop towards it over time, as more people subscribe.
The BT Wholesale checker can be found at: http://www.dslchecker.bt.com/
It should give you a range of speeds, and Plusnet's estimate is likely to be the bottom of the "clean" range.

[#2]

I can't find your account so I cannot do any tests, but personally I'd recommend it if the estimate suggests you'll get a large increase in speed.

[#3]

I've been on FTTC for a about one and a half years now and I'm seriously thinking about going back to copper. I initially had no end of problems with speed and many visits from BT engineers. The maximum speed I've ever achieved is 19M download, and since BT supposedly fixed the problem, I'm getting an average speed of 14-15M.  BT tell me that's as fast as I'll get because of my distance from the cabinet which is less than half a mile away, at this speed the extra cost for so called high speed fibre! is not worth it..