Those photos are perfect, thanks Malcolm, I can see exactly what you have.
I would describe the decor of your teapot as "Fancy Imari" rather than true Satsuma, but the differences often merge on this era of Japanese porcelain. It dates to the 1950s or 1960s when the Japanese perfected techniques for printing complex enamel patterns that did away with hand painting, though there may be a little 'heightening' of the colors here and there still done the old fashioned way by hand.
It depicts a pair of magpies, of course, as auspicious to the Japanese as they are in Europe, believed to be the bringers of good news. They are perched among tree peony blossoms or botan, also universally popular in the Asian tradition as bringers of wealth, health and eternal beauty, which pretty much covers all the bases!
The mark on the bottom is not one I've seen before, but then these Arita Imari decorators and import companies came and went with great rapidity at the time. The four character kanji seal reads (top right, bottom right, top left, bottom left):
恵称 Megumisho (the maker)
春己 'Spring treasure'
As for value, this era of fancy Imari porcelain is not quite old enough yet to have developed much collector premium and its value is purely decorative.
If you saw your teapot for sale in an antique shop it would be priced at about US$100.
Expect to get 30% - 40% of this if you were to sell at auction or on line (eBay etc).
I do hope this helps!
Please let me know if you'd like me to explain or expand on any of the above, I would be glad to.