JSFiddle - React, Tailwind, and code Playground

HTML

<label for="broker_fees">Broker Fees</label>
<span class="gbp">
    <input type="number" placeholder="Enter whole GBP (&pound;) or zero for none" min="0" max="10000" step="any" value="19.99" name="Broker_Fees" id="broker_fees" required="required" />
</span>

CSS

span.gbp {
    float:left; 
    text-align:left;
    position: relative;
}

span.gbp::before {
    position: absolute; 
    content: "\00a3"; /* £ */
    padding:3px 4px 3px 3px;
    left: 0;
    top:0;
    bottom:0;
}

span.gbp input {
    width:280px !important;
    padding-left: 15px;
}