Insulating the loft and cavity wall insulation are 2 essentials to keeping the house warm and energy costs down.
I wanted cavity wall insulation in the early 80's in a previous house, but had a lot of objection from my hubby, father in law and Uncle Tom Cobbly and all. But I had my way (ok, I usually do) and had it done with mineral wool. It cost me �300, quite a bit then. But we were in that house for 23 years, it was incredibly cosy, and saved a lot of money on heating bills.
I've just had the cavity done in my bungalow. I can feel the difference already in heat retention, particularly in one bedroom. Chatting with the surveyor he said the 'mustn't breach the cavity' objections were still there, and come mainly from builders!
Get it done. It's cheap, you will save money and not take years to recoup the cost. And ensure your loft insulation is to the max as well.