The misprints spell "Not even the beginning of the end" (Churchill), which continues "but it is, perhaps, the end of the beginning". Each across answer is a word beginning with prefix. Using the continuation of the quotation as a hint, take the end letter of each prefix, spelling THIS LABOUR WILL BE WELCOME. With the concluding words "HONOURED FRIEND", this is the final line of the first book of Wordsworth's Prelude. As per the instructions, call in the answer FRIEND.
Across:
1. UT=note + MO=moment + ST=silence
7. TIW=god rev. + HAL=prince
13. P(ressure) + O="a round" in BID
18. T=to + RANSOM
19. LID=top in COLE=cabbage
20. AGO(N)
21. (th)AT in ABLE
22. C=century + O=of + OP=work
23. RISES UP anag.
24. FORB=that which is not grass + I(n) + D=semicircle
25. LOWS=depressions in BET=lay + AIRS=winds; ref. 'Upstairs, Downstairs'
27. homophone: BUY CEREAL "for the ears"
30. FOR=on account of in MALM=chalky earth + E(xpose)D
32. ILL=with difficulty + APSE=extreme point in orbit + D=day
36. A + HO=prostitute in BR=brother
39. TIDE=trend rev.
41. OWE=bear in HOLLY=evergreen + E(at) + D(rink)
44. EP=record in PROSE=plain language
45. NATION + ALLIE(s) anag.
46. CROCUS anag.
47. AP=to be eaten (as per doctor's orders) before a meal + O=of + CARP=fish
48. I'M BOSS
49. reversed container &lit.
Down:
1. TUFA: "Deposits from lime", anag. FAUCET less CE=safety marking
2. ORBIT: "Regular beat"; OR BIT
3. MARL: "Bind, as one does with rope"; MAR + L(anyard)
4. BEANO: "Bash"; container
5. SOPRANIST: "Singer"; RANI=princess in POSTS anag.
6. DOTE: "to love without passion"; DOT + E(urope)
7. WEBCAM: "Net device"; B(o)W CAME anag.
8. EOLIC: "Lesbian poet's langauge"; LEO anag. + I C
9. MOLTO: "Very"; MOLT + (n)O(t)
10. BHOPAL: "Historic state"; HOP=fly in LAB rev.
11. WALLS: "linings"; W=women's + ALLS
12. FUSIL: "Milton's cast"; container
13. SODBUSTER: "one who hoes Stateside"; D(eparting) in SOB + US + TER(m)
14. RICEPAPER: "edible substance from tree"; PAP + E=English in RICER
15. PIA: "Professing belief"; I=in in PA=Harrisburg area
16. ROGER: "Message received"; reverse container
17. DOSE: "Give portions to"; DO=to suffice + S(om)E
26. MEDICO: "Lister was one"; ME=most exc.+D(eveloping)+I=int'+CO=company
27. BAHAI: "religion from Iran"; HA(j) in BA=Egyptian soul + I=one
28. LOLLS: "Dangles"; L(ittora)L in LOS
29. WEIRS: "they get stuck into rivers"; WIRES anag.
31. ROTED: "conned"; container
33. POLL: "register"; double definition
34. LAIC: "Not professional"; (so)CIAL(ly) reversed
35. TIDY: "fair"; (securit)Y + DIT reversed
36. AMIE: "bit on the side"; MA reversed + I.E.=that is
37. PHON: "It measures what you hear"; pH=measure of tartness + ON=subject to
38. ROSS: "Supremes lead"; G=government removed from GROSS
40. POIS: "Marae might have witnessed dance involving these"; POIS(e)
42. PEA: "plant"; container
43. BOD: "Dude"; B(lunders) + 'OD