I would not suggest necessarily being limited to the internal Ipad GPS, which (for me) is crap in some planes and works OK in others.
There are external units (e.g. the XGPS150) which got past the Apple Politburo restrictive practices on bluetooth and which work very well, and a product which did good SV would make it worth installing an XGPS150 properly - with velcro, of course 
Currently I have a genuine-velcro-installed Emtac NMEA bluetooth GPS which is nicely out of the way, has its own rooftop antenna and drives any portable device in the cockpit - except of course Jobs' deliberately incompatible creations which would need a second such device to be installed separately. There is currently no Ipad compatible GPS which has an external antenna input (AFAIK) but usually if you velcro such a device on top of the instrument panel it will work well enough. Then one just needs to bring +5V to it via a USB cable, from another "velcro installed" 5V power unit. This isn't hard.
And it's easy to have enough FLASH in the unit to hold the entire world SRTM database, but one would not need the whole world in one go.
All external GPS units seem to at least augment the CoreLocation services Apple provide. As far as I know, most just work: connect to iPad in BT settings and they'll start augmenting your location data. That means they work for UkRunways too.
We've looked at integrating with two different BT GPS units in the past, using their additional features. They usually have some extra functions if you use BT directly with them. By the time we had it integrated into OzRunways, the both models had stopped selling.
However, it may be desirable to disable the internal GPS if using the external one, otherwise the app may fall back to the internal one silently. I don't know if there is any control over this.
The only way I know of disabling the internal GPS is by putting the Ipad in the Air mode, which disables 3G, WIFI and GPS but leaves bluetooth running.
The only way to do that is to ignore CoreLocation in our software and connect to the BT GPS directly. If you disable location services, any connected BT GPS will stop updating location as well.
When the dust settles and most things we have in OzRunways work for UkRunways, I'll have another look at this.
I'd have to do an inventory of current models.
Are you going to offer an Android app?
Android version... frankly - we're unsure. If there's enough market, yes.
Why do many flight planning & navigation providers choose so unfortunate names for their products? I mean, Skydemon is an unfortunate one, but UKRunways seems even more unfortunate...
Just my 2 cents...
I am sure you will do your research and soon find out. I understand the Android tablets are outselling IOS tablets at the moment, but I suppose pilots are a non-standard section of the consumer market.
I recently bought a Nexus 7 tablet at around half the price of the equivalent iPad mini. It seems to work just as well so far.
I recall reading that Skydemon started as something else (SkyAngel or something like that?) but got threatened by somebody with a similar name so they had to change it.
I would think that Android was the way to go for a new development because Apple have a huge battle on their hands to rebuild, never mind maintain, their market share. They have only one way to go from where they are and that is downwards.
But IOS is a big market right now and cannot be ignored, and you benefit from a relatively constant platform to target.
Just my opinion of course 
It is great there is another product. But this is a crowded space and I won't look at anything unless it runs on my Android tablet. I have an ipad purely for Jepp View. And I will drop that as soon as they port to Android.
I don't see any USP in this product from the way it is described. While I think SkyDemon can be over-egged on fora such as this, it is your competitor - how are you different?
