No, I've not gone to the dark side of horse ownership and related wheeled things; I'm talking shipping your windows and hatches...
The best insurance against damage is to ensure you package the goods as well as you can. This means padding around the edges, particularly any sharp corners which should be supported (eg in a wooden sleeve). Use quality double wall cardboard or a suitable box, but make sure the packing prevents them from rattling around. If glass, put several layers of card or other padding to the outer surfaces. Pack as if you expect the box to get dropped. It probably won't, but....
We have a blanket policy which covers the UK and Ireland (only) subject to a £250 excess. This applies to all shipments arranged by us. If there is a loss, sadly you bear the first £250, but then again we have the hassle of processing the claim.
We use UPS and Parcel Force. Both will insure up to the value specified, often termed the 'declared value'. The insurance charge is calculated as a percentage of the declared value (UPS 1%, Parcel Force 0.8%, both plus VAT). The declared value has to be specified when the shipping is booked. Generally speaking we don't use declared value or courier insurance, but if you want to and/or your shipment is international you have this option. We will expect you to specify the value.
For international clients, another consideration is that customs may use the declared value as the basis for calculating any tax or duty they consider due. In theory, if the goods are being refurbished as a 'temporary import' then tax and duty should not apply to the 'value', but only if the courier/HMRC processes this correctly.
Duty of care
In principle, whether goods are insured or not a courier should have a duty of care to treat goods with care and respect and not allow them to be lost or damaged due to negligence or similar. However, trying to attach such a claim to the sloping shoulders of large fortress/machine based couriers is a thankless task. Not impossible, but a task I'm afraid I won't have time for. If you have the time go for it...
Some recent, but fortunately isolated cases have opened my eyes to the small print in courier contracts, so it's important to understand these. I'm quoting for UPS but all are similar.
So, if you don't insure and your goods are damaged, the limit UPS will pay is £60 per item, plus the shipping cost. To them it matters not that your goods were worth more.
If your goods are lost, then the payment is based on weight, plus the shipping cost. We had an unfortunate case where a yard sent in some windows in a wooden crate. The quoted weight was 44kg (which I suspect was over stated). UPS lost the crate (it's probably being used as a coffee table in a depot somewhere). It contained four windows. In the end we had to get some new ones made, costing ~£1,500. UPS calculated the pay out as less than £500 leaving the client to bear the additional £1,000 in spite of the fact that UPS accepted they were totally at fault. When I challenged this they just pointed to a zero 'declared value'.
So the moral is this. If you want the courier to take full responsibility you must specify the value and pay for their insurance. Even then you've still got the hassle of trying to break through to fortress UPS etc to make and pursue your claim.
The best insurance is to pack well. Few parcels get lost and in over two years we've only had one lost and one badly damaged. If we arrange the booking then your exposure should be a maximum of £250, but if you want more cover, please ask and we'll add the courier premium. It is sad that in todays market these large companies have such sloping shoulders, but that's progress for you. Hopefully you will find us more old school.