I don't know the value of your heritage pens..........for repair in the long run it don't really matter if your pens are run of the mill. They were good enough for Gramps when he was young. It could well be you have good to great nibs.
I looked at buying a Swan for some 3 months in Swan had a great range of flexes in it's nibs, from nail all the way out to superflex, before finding a no name German pen for a cheap price. I live in Germany.
A decade and more ago....'flexi' was a much bigger foggy word back then...stretching some four flex rates of today's definitions. All I knew was some to many of the Swan pens were 'flexi' and more flexible than semi-flex.
Do go to other European brands on the com and ask there if no good answer to price comes up.
Don't know English made Parkers but I have a '50's English made Jr. Duofold with a semi-flex nib. That was when in America all Parker's were made as nails...the semi-nail P-75 came later.
So it is quite possible you have real nice nibs. And even faster today if one uses Noodler inks. Reputable repairmen say that! I take their word and save money and heartbreak. There are more than enough non supersaturated inks in the world.
You will have to have those pens re-sacked....the rubber sacs die after 30-40 years.
I once had a good fistfull of lever/sac pens but got into piston pens. Lever pens are the fastest pen to reload, and are light and nimble, posted with the great balance demanded by the buyer in days of yore. I still have three or four.
There is a gold polish cloth that is not very expensive for the nibs.
One should see if there is any writing on the pen bodies.
One will be able to finger polish the brass and body, with using only your fingers....no cloth and some Semi-Chrome or a light chrome polish. Do not use a cloth to put the polish on and tape over the names on the pen bodies. Polish two-four tjmes and buff off with a flannel cloth.
Until recently when everyone bought cheap Chinese pens instead of cheap vintage pens, polish threads were quite common.
Once a bit polished up, your heritage pens will look much better, and getting them re-sacked is cheap..........if handy you could do it your self, there is enough instruction how to do that here on the com in old threads, but I don't really think it's worth gathering the material for just two pens, that you do not want to break one it belonged to your grandfolks.
Clean, re-sac and think good thoughts of your ancestors, could still be good to show and leave to your grandkids.
Don't worry about the worth.....they probably won't buy you a proper hangover.