Defensive problems!!

i'm just coming up to january in the first season with blackpool and i'm sat in fifth in the table which i'm reasonably happy with. although i could be doing so much better if my defence was stronger! I've been conceeding 4 goals to teams like scunthorpe but still winning by scoring six! So just wondering if anybody has any ideas for some great defenders that i can bring in to tighten up the defence that are reasonably cheap? Also maybe an option for a striker as freddie sears has just been injured for 2 months who i have on loan thanks for the help anybody