Not quite as popular collectible as, say, The Victor perhaps but growing in stature thanks to eBay UK. The free gift Kestrel Glider is fairly common and is occasionally offered separately on eBay UK for £30 to £40-ish. Add this to the values below if intact and still in package.
A copy of #1 sold on eBay UK back in Jan 2009 for £46. Nice condition with two minor splits on the front cover. A very nice run of #1-50 with the free gifts in #1-4 sold for £459 in 2004 on eBay UK.
Note: some PR issues may have no value. Selected issues in FN, VF or VF/NM may not exist in some titles.