I don't actually own a 3G/4G router, but I read about the TP-Link TL-MR3420 and it appears to be a relatively good device. It has Wireless N connectivity at 300 Mbps. It's available for under £27 new on Amazon.
Though, it is worth taking note that for 4G you will need version 2.0 of this router.
Prior to purchasing, you may want to check to see if your dongle is compatible. You can find this out at the product information page.