My router is no more?

[#1]

My specific problem is clusters of disconnections that may happen at certain times of day, the most obvious one being sometime between 6am and 8am, but it seems like an intermittent fault.
For further information: I use a faceplate splitter NOT microfilters, and as it happens I can't find a microfilter right now because I think I gave them away after fitting the splitter.
I use a router not a modem.
Now I do have a spare ADSL modem but its of uncertain condition and I don't relish the prospect of crouching in our hallway to run the connection for the two hours or so to have a fair chance of the fault showing.
When a previously rock-solid connection goes bad and I am unaware of any changes here my first response is to blame the phone line, it's given trouble before.
What should I do?

[#2]

Sounds similar to my fault other than i get dropped throughout the day, often getting much worse at night.
You really should try and check everything you can, as if BT are called out and they show the fault is actually in your house they may charge a £144+VAT call out fee (£170 in total), which is not nice.
I have tried everything possible e.g. unplugging everything, trying a modem I had rather than my router, swapped the filters. The fault still occurs, but at least i've done all I possibly can to rule out the house. I've now got BT coming out on Monday to do a line health check but I will be running all the tests again this weekend to double check everything.

[#3]

OK that's good advice. I'll work on it...
I've tried it direct with no filter at all, still bad.
I'm trying a different router now, its a Draytek Vigor 2600. Anyone know how to get an error log from it? Let me guess, I need to use syslog?
Update: After a couple of hours I THINK I'm looking at a clean log but I'm not certain.

[#4]

After my previous comments I now appear to have gone a week without observing any problems, so maybe my router has miraculously fixed itself or perhaps I've moved something that was causing a problem.