UKC

I am a very inexperienced skier but I intend to get back into it more next year. I suffer from poor (non-existent!) dorsiflexion i.e. my ankles don't really bend forwards. As you might expect this is pretty inconvenient for skiing.

I have my own skis & boots & I'm not afraid to mess with them a bit. Is it possible to install a plastic wedge or similar under the heel binding to cant the boot forward a few degrees?

I'm thinking if I also put a wedge heel insert between liner & boot then both together might help a lot.

short answer is yes, it's possile to shim between bingings and skis. depenign on your bindings there might be oem mounting plates, and or remove any existign mounting plate from under the toe unit. 

it's also possible to unscrew the bindings from the skis, assuming they're not perma-glued in, and re-mount using the same holes. opinions on this vary, and some people like to add glue to the screw threads whne they do this. sometines even on the first install, althogh that's (ime) rare. 

if you're doing diy, be carefull of screw length. I'v demounted and remounted bindings before, and with care managed (I think) to re-thread the screws into the same thread. rotate the screw anticlockwise and try feel the nub of hte thread before you turn clockwize. If you're changing screw length this might be a tad more tricky.

If you know a good ski shop (emphasise good!) I'd have a chat with them to get view on what's sensible. 

Yes, you can buy heel lifts to insert in the boot. That’s going to be a cheap and easy thing to try. Some boots allow you to change the forward lean. So I’d look at that as well before messing with the bindings, which is also possible but not without risks if you do it yourself, as the previous poster said. 

With the forward lean thing, think about what you are trying to achieve. There is a conflict here between being comfortable in your boots and getting your weight forward. It's very tempting to think that you need to get your weight forward and to increase the forward lean - however my experience was that this just made my boots really painful because they were forcing me to maintain a position that was beyond my usual range of motion. Conversely, I found that reducing my forward lean helped more because then I was able to wear my boots for more than half an hour at a time and to work within my natural range of motion.

I used heel lifts in my old boots, which helped. I had to get the instep buckles of my boots adjusted to accommodate the extra volume. However, last time I got new boots I was able to work with a good boot fitter who was able to help me find something comfortable that I was able to use with no modifications beyond getting the liner moulded.

I would agree to try heel lifts in your boots before messing with your bindings. That should give you an indication if the general approach is going to work and is less risky that messing with your bindings. However, various methods of shimming bindings are possible, as described above. I am happy with my shift bindings as they are, but I have shimmed my pin bindings using a manufacturer-supplied kit.

Finally, next time you buy bindings, pay attention to the delta, or the degree of heel lift built into the binding, as this varies between bindings. This isn't usually easily adjustable, but the delta is usually quoted in the binding specs. If you are sensitive to heel raise, take this into account when purchasing bindings.

I have particularly poor dorsiflection in one ankle due to bone callus after a nasty fracture. I have a half inch heel lift in one boot to overcome this in order to get weight over front of my skis. It took a while to find a boot with sufficient instep height to accommodate this. The solution works well for me and I don’t need any other mods to my bindings etc. In my opinion there are only a handful of ski boot fitters in the UK capable of doing this sort of work well. If your existing boots and foot beds can’t be modified then a new pair from one of those reputable boot fitters may be a necessary but worthwhile investment. Ski shops will be getting their new stock in soon so best to go early while they have lots of stock and more time (allow half a day for a fitting). I see you are in Barnsley. Backcountry UK in Otley may be able to help, but for my money Rivington Alpine in Chorley is the best and well worth the drive. If you are fortunate they may be able to modify your existing boots and just supply the lifts and new foot beds.

As an aside, modifying binding ramp angle would mean always having to get the right ski on right foot, embarrassing if you get it wrong!