I bought my Australian saddle (very similar to English) fitted for my mare. My gelding has the same angle to his withers (measured in degrees), but his shoulders are narrower. Therefor the front falls down, leaving at best a finger of clearance. It is made worse because his withers extend further into his back, so the saddle definitely rubs.
It is hard to describe, but look at this picture of a western saddle:
When people talk saddle width, they are normally talking ANGLE, as in the picture. However, gullets can also vary in how many inches there are between the bars (the horizontal part of the blue line). I know English saddles look different, but the principle is the same. A gullet that is 7.25 inches between the bars will ride lower on a horse whose shoulders only provide 6.75" of separation in that area.
When I tried a Wintec pad, it raised the whole saddle up too far into the air. So I cut it in half, and used just the front. That worked fairly well. It essentially added a half inch plus to the gelding's shoulder where the gullet lays. With some practice, I ended up using this: Fleece Western Wider Wither Pad - Statelinetack.com
I place it on the hollow at his shoulder, and put the load bearing part of the saddle right on top. It changes the angle of the saddle (front to rear, not sideways) enough to clear the rear of his withers, and makes his shoulders wider so the saddle fits him well. It made a very obvious difference in how he moves and his willingness to extend.
Here is what you can try without spending any money:
Take a bath towel and fold it in half. Then fold it again, but not equally. You will end up with a folded towel that is 4 layers thick for about 9-10 inches, then 2 layers thick, then ends. Use it with your saddle and see if it gives you enough clearance. Ride, and see how your horse moves. Wither relief pads come in different thicknesses, so you could even try adding a hand towel in the 4 layer section to make it a bit thicker.
If it doesn't help, then a wither pad probably won't. If it does, then you can sew the edges of the towel, or spring $8 for a wither pad.
It is important that the angle of the saddle match the angle of your horse's shoulder, as seen from the front. My English saddles have interchangeable gullets, but all the gullets change is the angle. They are all the same width, in terms of the horizontal distance between the sides.
If the angle is wrong, it can lower the front of the saddle and nothing will make it right except a different saddle (or gullet, if yours can be changed). If your horse's shoulders are narrower than the horse the saddle was meant for, then adding bulk to the shoulder area seems to work well.
For me, the full length wither pads place me too far from the horse's back, and I don't like them.