We got it done last spring. Eventually. But, since the house belongs to my MIL, we didn't have to worry about the intricacies of the funding.
My MIL got a phone call early in March, asking if she was interested. She asked specifically if the loft would need to be cleared out or anything before they came to do it. The guy on the phone told her no, she didn't need to do anything. So, we were the first house on the schedule for when the team arrived from the mainland.
Except that the team missed the ferry. So, they got here late, and we were rescheduled for the end of the contract, several weeks later. Then, when they showed up, they took one look into the loft and said 'oh, we can't do anything. There's too much stuff in the way' and left.
We found out later that, apparently, they'd spent their entire 2 months here being kicked out of one hotel after another for drinking/drug use, never paid their bills ('oh, the company is supposed pay'), and despite charging the Comhairle (or whomever was paying the subsidy that time) for each house on the list, found reasons they couldn't actually do the work on most of them. Thankfully, at least they never charged us. If they'd put in any insulation (or pretended to) it would have cost £200.
Luckily, a few months later, someone came by from the utility company to survey the houses who'd requested the loft insulation, and see if it had actually been done. And when we told him it hadn't, he said we were eligible for a different scheme, and it wouldn't cost us anything. A few weeks later, a couple of boys from Stornoway came down, and had it finished in a couple of hours.
I definitely recommend getting the insulation put in. It's made a HUGE difference in the comfort in the house. But do be a bit careful about the various contractors. Ask around, see if anyone else in your area has any experience with them.