It's erroneous to say those Celtic components represent British & Irish admixture though as they don't. You would need Bronze Age British samples to represent actual British & Irish.
Code:
England_CA_EBA,0.124636,0.125926,0.061576,0.062106,0.031134,0.019724,0.004296,0.004654,-0.000216,-0.004323,-0.004872,0.005928,-0.011678,-0.015398,0.025123,0.010342,-0.003593,0.000718,0.002905,0.006107,0.005359,0.002899,-0.000383,0.003294,-0.001058
England_EMBA,0.125205,0.129988,0.060716,0.06137,0.029236,0.020359,0.012691,0.002077,0.002659,-0.005103,-0.002273,0.003447,-0.010406,-0.01445,0.029587,-0.005834,-0.020601,0.008868,0.003017,0.001,0.002371,-0.001484,-0.008134,0.008435,0.003832
England_IA,0.13175,0.130749,0.060151,0.048046,0.035083,0.02015,0.004818,0.003692,0.004244,0.004191,-0.004425,0.005732,-0.010518,-0.018476,0.018017,0.010044,0.001206,-6.3e-05,0.003331,0.003908,0.003899,0.000247,-0.001202,0.011417,0.000449
England_LBA,0.119514,0.116786,0.056945,0.05814,0.031698,0.018686,0.00235,-0.003461,0.004909,-0.00656,-0.006496,0.003447,-0.025718,-0.004817,0.019544,0.02148,0.00352,-0.000253,-0.000126,0.006128,0.005989,-0.00272,-0.001602,0.012291,-0.004311
England_MBA,0.127013,0.129092,0.063068,0.059755,0.034178,0.019916,0.001493,0.004927,0.004596,-0.001394,-0.004738,0.003967,-0.01115,-0.015657,0.024677,0.009157,-0.005952,0.00307,0.000983,0.003987,0.004698,0.004713,-0.000638,0.005834,-0.001205
England_Roman,0.127482,0.136806,0.059585,0.049465,0.03715,0.017052,0.003659,0.005241,0.003009,0.00315,-0.005382,0.007108,-0.014208,-0.01276,0.021967,0.001762,-0.008382,0.001122,0.003951,0.003805,0.005259,0.001661,-0.003504,0.007195,-0.000239
England_Saxon,0.132462,0.13405,0.063875,0.056929,0.041162,0.020568,0.006257,0.006894,0.003988,-0.002415,-0.004933,0.004552,-0.009291,-0.012455,0.024243,0.011237,-0.00308,0.001504,0.005201,0.006659,0.005334,0.002473,-0.001648,0.016644,-0.000868
This is what I get using 0.5 with these samples added.
Target: Grace
Distance: 0.9439% / 0.00943869 | ADC: 0.5x RC
63.0 England_Roman
21.8 England_Saxon
15.2 Germanic
I think Creoda might be better at suggesting some samples but Continental Celtic is definitely not representing British & Irish ancestry. It represents Continental Celtic ancestry.