Internet upgrade

I've been using Eircom Home Plus for a long time. Its download and upload speeds (actual rather than what they're supposed to be): 1650 kbps/200 kbps.
I had talked quite a bit to Eircom as to why I wasn't getting the advertised 2048/256 speeds and they claimed that anything upwards of 80% of the nominal rate was considered OK. They claimed that distance from the exchange mad a big difference to what actual speeds were attainable.
In any event, they have been promising that this package (Home Plus) will be updated before the end of the summer to 3072 kbps but that hasn't happened yet.
So, yesterday, I upgraded to Home Professional which has advertised speeds of 3072/384. What's more, this package will be upgraded to 7782/672 sometime very soon (they even said it might be this week).
In any event, my speed went up today. First to something like 2150/470. So, as it hadn't reached to where I expected, I called them and, after looking at the data, they concluded there was an error in something or other. They fixed this quickly and I immediately starting getting speeds of 3150/285. So this was a huge jump and I was very pleased with this, particularly as an even greater jump was likely very soon.
It's interesting to note that the attained download speed was actually GREATER than the advertised d/l speed of 3072 kbps which might suggest that whatever my distance from the exchange it shouldn't prevent me getting a high d/l speed.
Another possibility becomes obvious looking at the d/l&u/l speeds attained in the two instances quoted: 2150/470 and 3150/285 versus advertised of 3072/384. This seems to indicate that they can fiddle around with the upload/download speed combinations. So, if upload is high, d/l comes down a lot.
Anyway, these good speeds persisted for a couple of hours and then, without warning, both deteriorated. Right now we are getting 1800/270. Looks like I'm going to have to talk to them again tomorrow.