Solving time 20 minutes

About average level of difficulty with no real obscurities. 5D is strange and I can't help feeling I'm missing something subtle. I also don't really understand the cryptic to 8D

The end of June 2012 marks the 50th anniversary of my learning to program the ICL 1301 computer, which was when I learned about Alan Turing. June 23rd was the 100th anniversary of his birth and I can't let it pass without an acknowledgement to him and his immeasurable contribution to our lives without which this blog would not be possible

Across
1	CANNES - sounds like "can" to the French; Nice in France;
5	WHISTLER - (the swirl)*; James Whistler 1834-1903 who painted pieces of music and mothers;
9	OLD,WINDSOR - (lord)* surrounds WINDS-O; over=O (cricket - what else?); Thames-side village near Windsor;
10	FOIL - F-OIL; fine=F; sun lotion (perhaps!)=OIL; fencers cavort on a piste;
11	STRATEGY - STY surrounds (great)*; does the Euro Area have one?;
12	GEYSER - GREY-SE then move R=queen to the rear; as featured in Yellowstone National Park;
13	JACK - two meanings 1=sailor; 2=small ball used as a target in bowls;
15	ULTERIOR - UL(s)TE(RIO)R; the most interesting motive;
18	REST,HOME - REST-HO(M)E; (the) excess=(the) REST; not where I want to end up;
19	BOAR - BOA-(freeze)R; Tamworth no doubt;
21	ENAMEL - LE(MAN)E all reversed; what the hygenist cleans;
23	EQUALISE - cryptic definition; park=slang for football pitch;
25	UNDO - hidden (Ness)UN-DO(rma);
26	GREGARIOUS - GR(I-RAGE reversed)OUS(e); bitch=moan=grouse;
27	ASSIGNEE - ASS-GI reversed-NEE; charlie=slang for fool;
28	EL,NINO - (l)E(y)L(a)N(d)I(i)-NO; quinquennial movement in the South Pacific;
Down
2	ALLOT - (sh)ALLOT;
3	NEWMARKET - NEW-MARKET; also a famous centre for horse racing;
4	SINGER - SIN-(pon)G-E-R; Isaac Merritt Singer 1811-1875 who invented the Singer Sewing Machine;
5	WISH,YOU,WERE,HERE - insincere message people sent before texting was invented;
6	IRRIGATE - (b)IR(d)-R(e)IGATE;
7	TUFTY - TU(F)T-Y(oga); following=F; road safety conscious squirrel;
8	EMILE,ZOLA - ALO(Z)E-LIME; what is an aloe-lime?; French writer and saviour of Dreyfus;
14	APENNINES - A-PENNI(N)ES; N from (woma)N;
16	REBELLION - (beer)*-ILL reversed-ON; last resort of slaves, peasants and poll-tax payers;
17	HOOLIGAN - HO(OLI)GAN; OLI from (s)OLI(d); golfer Ben Hogan 1912-1997; idiotic follower of football;
20	CURATE - two meanings 1=pastor 2=manager of museum;
22	MAORI - I-ROAM reversed; author=I(?);
24	SPURN - S-PU(R)N;