Price is not always the best guide , prices asked by some dealers are to be blunt laughable .Ask yourself this , do you want a gun that just looks good or do you want a gun that will do good service over the net 30 years ? I see many older and very pretty English side locks that are way past there best like a classic car that has had a cheap rebuild ,fine to take out for a spin on nice afternoon but that's about all .
Hate to say it but if you had come into my shop and asked the same question I would have said that you should consider an AyA No 1 or 2 , reasonable build quality 2&3/4" chamber that is always an advantage ,spares should they be needed are readily available and I see AyA's that were made in the early 60's still in regular use . There are better finished guns but in my experience they all fall short of the AyA mechanically , some Spanish made side locks are notorious for having uneven and thin walls .
As much as I would like you to buy a fine English side lock and there are many out there to be bought,but due to age and poor maintenance many are just not up to the job .