Need ID of bird seen in my garden this morning

I have a trellis about 7 feet high on which I have sweet peas that have aphids, mostly greenfly.  About 7.30am today I noticed a very small bird flitting about in there which I presumed it to be a wren because it was tiny, brown and the way it moved I presumed it to be a wren. However, then I saw that it did not have the tail of a wren and also was very pale cream on its underparts.  Can someone help with the Identity please?