Hi Ian,
I think that for a “Definitive” answer to your question there are quite a few things one would need to know. Like how well your service provider actually functions in your area, or is there something wrong with your hardware i.e router, or are you sitting next to a microwave? 🙂 In any case this trouble shooting process may help you:
System Preferences > Network > (bottom of window) Assist me… > Diagnostics…
Follow the prompts.
You might need to do this a few times a day. Sometimes it tells me to restart the modem/Airport. Just turn it off wait a few seconds and turn it back on. A new connection should start.
Best,
Nick
