The UK copyright Act has the concept of "fair dealing" which is more restricted that the US concept of "fair use".
For your purposes, Section 30 appears to be applicable:
30 Criticism, review and news reporting.
(1) Fair dealing with a work for the purpose of criticism or review, of that or another work or of a performance of a work, does not infringe any copyright in the work provided that it is accompanied by a sufficient acknowledgement and provided that the work has been made available to the public.
(1A) For the purposes of subsection (1) a work has been made available to the public if it has been made available by any means, including—
(a) the issue of copies to the public;
(b) making the work available by means of an electronic retrieval system;
(c) the rental or lending of copies of the work to the public;
(d) the performance, exhibition, playing or showing of the work in public;
(e) the communication to the public of the work,
but in determining generally for the purposes of that subsection whether a work has been made available to the public no account shall be taken of any unauthorised act.
For your reviews, you would need to properly attribute the source of the image that you were using and that source must be legitimate. If you can't find a clear legal pathway from the image you have to the actual copyright holder you could be in trouble (e.g. an image from someone else's blog where that image may have been uploaded illegally). Your best bet is to go to the studio concerned and use images from their official public releases with proper attribution.