I don't think you'll get an all in one tool to many things can cause slow internet, internal / external hardware or software, malware the exchange the line or isp throttling ect ect so many things.
The only way is to start with your pc and work your way through every thing in the network using different tools.
Out side the house really is the ISP's domain some do have free tools that you can use yourself to check the line and for problems from the house upto but not normally inside the exchange.
Here is What I'd do to start with.
1: Check for Malware
2: Check the Networkcard
3: Check no new installed programs are hogging the bandwidth and slowing things down. (you'd be amazed how many things use the net even when you think they are not active.)
4: Give pc a spring clean temp files off and defragment just so your running at 100%.
5: Check router the settings are all OK.
6: Check all the wiring in your internal network signs of ware and for loose connections everything wants to be firmly in.
7: Check for corrosion or damage inside wall sockets.
8: Take a look outside where your line connects to the house for any sign of dmg.
9: Ping the exchange to check for any signs of packet loss.