Bad luck with the write-off.
Never accept their first offer, as others have indicated unless it's for teh invoice amount.
I have had 2 bike written off in recent years. First was an accident on a Boxer Cup in 2004 and second was stolen-recovered R1200s in 2007. On the R1200s they offerred me £8620 which I immediately turned down, sent in pics of the bike and also adverts from mags etc. They then offerred £9250 which I turned down again, threatening with the Insurance Ombudsman.
Final offer of £10150 accepted. The bike was 5 months old, had 1500 miles on it and numeropus spares which I'd declared.
The BCR in 2004 was a different matter. They offerred £8150 which I turned down. One phone call later, £8450 and money in bank within a couple of weeks.
Cat A and B write-offs are only any use if you intend to break them. Cat C you needa proper ministry test to get it back on the road and Cat D you need an MOT regardless of age of the bike. I bought back both bikes and again dont be afraid to negotiate. the BCR they charged me 30% of the payout value. The 1200s they wanted 3850 but I argued the toss and they accepted 3250. Im still in negotiations however as they have thrown away the headlight, clocks, mirrors and a couple of other bits, plus theyve damaged the bike in storage.
It's all down to negotiations. Best of luck