Back to the OP......
If you have a Record 405 that is complete except for the cutters, then expect to pay 40 - 50 quid for a good set in good order. It will enhance your plane. Having said that, I've only used 3 or 4 on a regular basis on my Record in the last 30 odd years.........
What's missing apart from cutters?
We had a member here a long time ago, called Alf, regrettably not posting any longer, who compiled a list of manufacturer's Manuals for all the various 'Boat Anchor' planes as she called them, on her web site, but if you search around there are manuals available on line or from member here which will detail what was included as standard in the Record 405
Finally, new blades.
It is possible to get new-made sets.... however, the ones that I have seen differ in one fundamental from the originals. Their shape.
They are rectangular in cross-section, whereas the original blades from all the old planes were trapezoidal - in other words the thin sides were very faintly slanted from the back to the front bevel side; it was only a degree or two and it may not seem important. However a trapezoidal blade allows you to hone the sides so that both corners of the bevel is pin-sharp from all three angles and it provides a tiny amount of lateral movement as the blade descends in its groove, reduces the friction on the sides and allows the fence clamped to the edge to direct the accuracy of the work - not the unforgiving shape of a rectangular blade locked in an unforgiving groove.
A small point, sometimes overlooked, but it's important.
Good luck