A compound of formula Ia: wherein: n is 1 or 2; R N is H or Me; R 1 is optionally one or more halo or methyl groups; R 2a and R 2b are independently selected from the group consisting of: (i) F; (ii) H; (iii) Me; and (iv) CH 2 OH; R 2c and R 2d (if present) are independently selected from the group consisting of: (i) F; (ii) H; (iii) Me; and (iv) CH 2 OH; R 3a and R 3b are independently selected from H and Me; R 4a is OH; R 4b is either H or Me; X is either N or CH; R 7 is selected from H and C 1-4 alkyl; (a) one of R 8a , R 8b , R 8c and R 8d is selected from H, halo, C 1-4 alkyl, C 1-4 alkoxy, NHC 1-4 alkyl; (b) another of R 8a , R 8b , R 8c and R 8d is selected from H, C 1-4 alkyl, C 1-4 fluoroalkyl, C 3-6 cycloalkyl, C 5-6 heteroaryl, C 5-6 heteroaryl methyl, C 4-6 heterocyclyl, C 4-6 heterocyclyl methyl, phenyl, benzyl, halo, amido, amidomethyl, acylamido, acylamidomethyl, C 1-4 alkyl ester, C 1-4 alkyl ester methyl, C 1-4 alkyl carbamoyl, C 1-4 alkyl carbamoyl methyl, C 1-4 alkylacyl, C 1-4 alkylacyl methyl, phenylcarbonyl, carboxy, carboxymethyl, ether, amino, amino methyl, sulfonamido, sulfonamino, sulfone, sulfoxide, nitrile and nitrilemethyl; (c) the others of R 8a , R 8b , R 8c and R 8d are H. n is 1 or 2; R N is H or Me; R 1 is optionally one or more halo or methyl groups; R 2a and R 2b are independently selected from the group consisting of: (i) F; (ii) H; (iii) Me; and (iv) CH 2 OH; (i) F; (ii) H; (iii) Me; and (iv) CH 2 OH; R 2c and R 2d (if present) are independently selected from the group consisting of: (i) F; (ii) H; (iii) Me; and (iv) CH 2 OH; (i) F; (ii) H; (iii) Me; and (iv) CH 2 OH; R 3a and R 3b are independently selected from H and Me; R 4a is OH; R 4b is either H or Me; X is either N or CH; R 7 is selected from H and C 1-4 alkyl; (a) one of R 8a , R 8b , R 8c and R 8d is selected from H, halo, C 1-4 alkyl, C 1-4 alkoxy, NHC 1-4 alkyl; (b) another of R 8a , R 8b , R 8c and R 8d is selected from H, C 1-4 alkyl, C 1-4 fluoroalkyl, C 3-6 cycloalkyl, C 5-6 heteroaryl, C 5-6 heteroaryl methyl, C 4-6 heterocyclyl, C 4-6 heterocyclyl methyl, phenyl, benzyl, halo, amido, amidomethyl, acylamido, acylamidomethyl, C 1-4 alkyl ester, C 1-4 alkyl ester methyl, C 1-4 alkyl carbamoyl, C 1-4 alkyl carbamoyl methyl, C 1-4 alkylacyl, C 1-4 alkylacyl methyl, phenylcarbonyl, carboxy, carboxymethyl, ether, amino, amino methyl, sulfonamido, sulfonamino, sulfone, sulfoxide, nitrile and nitrilemethyl; (c) the others of R 8a , R 8b , R 8c and R 8d are H. (a) one of R 8a , R 8b , R 8c and R 8d is selected from H, halo, C 1-4 alkyl, C 1-4 alkoxy, NHC 1-4 alkyl; (b) another of R 8a , R 8b , R 8c and R 8d is selected from H, C 1-4 alkyl, C 1-4 fluoroalkyl, C 3-6 cycloalkyl, C 5-6 heteroaryl, C 5-6 heteroaryl methyl, C 4-6 heterocyclyl, C 4-6 heterocyclyl methyl, phenyl, benzyl, halo, amido, amidomethyl, acylamido, acylamidomethyl, C 1-4 alkyl ester, C 1-4 alkyl ester methyl, C 1-4 alkyl carbamoyl, C 1-4 alkyl carbamoyl methyl, C 1-4 alkylacyl, C 1-4 alkylacyl methyl, phenylcarbonyl, carboxy, carboxymethyl, ether, amino, amino methyl, sulfonamido, sulfonamino, sulfone, sulfoxide, nitrile and nitrilemethyl; (c) the others of R 8a , R 8b , R 8c and R 8d are H. <EOS>