From 1meg to 8meg and back down to maybe 2meg

Having left a 1meg service and moved to to a 'up to 8meg' service, with dreadful results. (My ISP has raised a fault with BT), this is pending. In the meantime seeking information. If I leave this up to 8meg, and sign up with a 2meg provider, will this more or less give me a relatively stable (or near enough) 2meg.
I don't really want to have the annoyance, which I have had recently, with the present dismal service over days. Also don't wish to waste time and effort, waiting for the ISP's support to answer the call, and then be subject to a long 'question and answer' session. The questions and answers appear to be for the benefit of BT.
To have several days of a download speed of less than 1meg and then dropping to around 234meg for another two days would suggest to me that there is a fault somewhere. And yes, I have been down the 'three days' and 'ten days' retraining period and to leave the Router on permanently.

Depends, what are your SNR margin and attenuation figures.

Unable to obtain the figures with present Router Netgear DG632. Tried to obtain the figures using the guide as given by Bandbusy, but failed. I have another router Voyager 205, from which I have in the past obtained figures, but as advised, I cannot switch off the present router until the fault has been finalised with BT, so cannot change routers.
Since the fault was raised by my ISP with BT on Thursday 5th, there has been an increase in download speeds as shown here:
Thursday 5th, Ave 234mbps
Friday 6th, Ave 1.39mbps and today Sat 7th a large increase up to 2.7mbps (at 9.50am)
Have not heard from my ISP since Thursday, so do not know, if and what changes have been made by the parties concerned. will wait to see if the improvement holds/continues.
My side remains completely unchanged. Thanks for your response.

Further to last post. Have been in touch with ISP. They claim BT suffered a some sort of Major Outage. Also BT were due to Upgrade their VP on 6th Oct. Was showing Red prior to this. Lets hope things 'only get better'.