I'm the same Xray, but manage with "little and often". You can buy a type of flame-thrower weedkiller (not as alarming as it sounds) - a calor (presumably) gas canister on the end of a curved "walking stick" - you press and burn. No stooping required!

Get yourself a decent path weedkiller and a watering can to mix it in - Pathclear is okay, and Doff make one as well. Mix with water and use a fine rose to water onto the cracks, pick a dry day to do it, water every crack and crevice, regardless of whether its actually got weeds in it at the time. Be careful of run off onto any adjacent flowerbeds though. If you do it mid to late April, you should remain weed free till late summer/autumn.